Conceptual Physics Chapter 2 – Flashcards
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inertia
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the property of things to resist changes in motion
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newton's first law of motion ( the law of inertia)
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every object continues in a state of rest of uniform speed in a straight line unless acted on by a nonzero net force
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force
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in the simplest sense, a push or a pull
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net force
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the vector drawn to scale used to represent a vector quantity
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vector
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an arrow drawn to scale used to represent a vector quantity
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vector quantity
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a quantity that has both magnitude and direction, such as force
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scala quantity
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a quantity that has magnitude but not direction, such as mass and volume
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resultant
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the net result of a combination of two or more vectors
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mechanical equilibrium
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the state of an object or system of objects for which there are no changes in motion. In accord with Newton's first law, if an object is at rest, the state of rest persists. If an object is moving, its motion continues without change
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equilibrium rule
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for any object or system of objects in equilibrium, the sum of the forces acting equals zero.
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What relationship between the Sun and Earth did Copernicus formulate?
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The Earth revolved in a circle about the Sun.
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What two classes of motion did Aristotle advocate?
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Natural motion and violent motion
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What did Galileo discover in his legendary experiment on the Leaning Tower of Pisa?
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Galileo found that a heavier stone does not fall significantly faster than a lighter one.
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What did Galileo discover about moving bodies and force in his experiments with inclined planes?
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In the absence of a retarding force, a body will keep moving at a constant speed in a straight line forever.
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What did Copernicus say about the motion of the Sun?
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The Sun is stationary and Earth circles it.
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How does Newton's first law of motion relate to Galileo's concept of inertia?
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Newton refined Galileo's concept of inertia and made it his first law of motion.
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What type of path does a moving object follow in the absence of a force?
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It continues to move in a straight line at a constant speed.
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What is the net force on a cart that is pulled to the right with 100 pounds of force and to the left with 30 pounds of force?
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The net force is 70 pounds to the right.
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Why do we say that force is a vector quantity?
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A force has a magnitude and a direction.
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According to the parallelogram rule, what quantity is represented by the diagonal of a constructed parallelogram?
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The diagonal is the resultant, or sum, of two vectors.
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What is the resultant of a pair of one pound forces at right angles to each other?
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The resultant is a force of 1.41 pounds in a direction bisecting the 90-degree angle between the two vectors.
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What are the units for force?
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Force can be expressed in newtons or pounds.
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What is the net force on a bag pulled down by gravity with a force of 18 newtons and pulled upward by a rope with a force of 18 newtons?
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The net force is zero newtons.
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What does it mean to say something is in mechanical equilibrium?
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An object in mechanical equilibrium experiences a zero net force.
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State the equilibrium rule for forces in symbolic notation
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ΣF = 0
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Newton said that something was needed to change the motion of an object. A clear reading of his first law tells us that what is needed is ______.
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a non-zero net force
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Consider a book that weighs 15 N at rest on a flat table. How many newtons of support force does the table exert on the book?
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15 newtons up
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When you stand at rest on a bathroom scale, how does your weight compare with the support force from the scale?
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Your weight is equal in magnitude and opposite in direction to the support force from the scale.
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What is the net force when a pair of 5-N forces simultaneously act in the same direction on an object?
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10 N
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A bowling ball at rest is in equilibrium. Is the ball in equilibrium when it moves at constant speed in a straight-line path?
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Yes, the bowling ball is in equilibrium because ΣF = 0.
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What is the net force on an object in either static or dynamic equilibrium?
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The net force is zero.
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If you push on a crate with a horizontal force of 100 N and it slides at constant velocity, what is the magnitude and direction of the frictional force acting on the crate?
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The frictional force on the crate is 100 N opposite the direction of motion.
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Which of Newton's laws does the equilibrium rule illustrate?
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Newton's first law
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What concept was not understood in the 16th century when people couldn't conceive of a moving Earth?
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They did not understand inertia.
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A bird sitting in a tree is traveling at 30 km/s relative to the faraway Sun. When the bird drops to the ground below, does it still move at 30 km/s, or does this speed become zero?
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It continues to move at 30km/s relative to the Sun, but it has a speed of 0 km/s relative to the ground.
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Stand next to a wall that travels at 30 km/s relative to the Sun. With your feet on the ground, you also travel at the same 30 km/s. Do you maintain this speed when your feet leave the ground? What concept supports your answer?
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When you jump, you continue to move at 30 km/s due to your inertia.
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How much support force acts on a 200-N girl standing on a weighing scale?
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200 N
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A force of gravity pulls downward on a book on a table. What force prevents the book from accelerating downward?
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normal force
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If you pull horizontally on a crate with a force of 200 N, it slides across the floor in dynamic equilibrium. How much friction is acting on the crate?
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200 N
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Galileo taught us that if you roll a ball along a level surface it will
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keep rolling if friction is absent.
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A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is
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equal to its weight. equal to its weight divided by its mass. equal to its mass times its weight. ****none of the above****
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A hockey puck sliding across the ice finally comes to rest because
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of friction.
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The amount of force needed to sustain motion of a rock in outer space is
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a force less than its weight if friction is absent. a force equal to its weight. ****none of these****
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Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to
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follow a straight-line path.
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When you flick a card from beneath a coin that hardly moves, you're illustrating
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inertia.
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While you are standing in the aisle of a bus, the driver suddenly makes a left turn. You lurch to the right due to
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your tendency to keep moving forward.
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The resultant of a 40-N force at right angles to a 30-N force is
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50 N.
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When Nellie Newton hangs by the ends of a rope draped over a large pulley, the tension in each supporting vertical strand is
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half her weight
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The net force on any object in equilibrium is
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zero.
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Earth continually moves about 30 km/s through space, which means the wall you stand next to also is moving at 30 km/s. When you jump vertically the wall doesn't slam into you because
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you're moving horizontally just as fast as the wall.
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If you toss a coin straight upward while in a train moving at constant velocity, the coin will land
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as if you were at rest.
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The force that causes Earth to orbit the Sun is due to gravity, while the force needed to keep Earth moving as it circles the Sun is
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no force at all.
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An object in mechanical equilibrium is an object
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moving with constant velocity. having no changes in velocity. at rest. ****all of the above****
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Inertia is defined as a
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property of matter.
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When no forces act on moving objects their paths are normally
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straight lines.
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Monkey Mo hangs from the middle of a horizontal rope. Tension in the rope is greatest if the rope
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sags very little.
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The earliest and most influential Greek philosopher was Aristotle, who among many contributions taught that
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All motion is either natural or violent The four elements are earth, water, air and fire violent motion requires a sustained push or pull
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The gain in speed each second for freely falling object is about
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10m/s
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Science later greatly advanced when Galileo favored
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Experiment over philosophical discussions
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If no external forces act on a moving object it will
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continue moving at the same speed
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A hockey puck is set in motion across a frozen pond. If ice friction and air resistance are neglected, the force required to keep the puck sliding at constant velocity is
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Zero
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If gravity between the Sun and Earth suddenly vanished, Earth would continue moving in
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A straight-line path
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When you flick a card from beneath a coin that hardly moves, you're illustrating
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Inertia
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When a rocket ship gaining speed in outer space runs out of fuel it
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No longer gains speed
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Two students engaged in a tug-of-war each pull a rope in opposite directions with a force of 400N. The net force on the rope is
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Zero and rope tension is 400N
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A pair of wires support a heavy painting. Tension in the wires is greater when they are
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Not vertical
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When Nellie Newton hangs at rest in the middle of a clothesline, tensions will be the same in each side of the rope when
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The angles for both sides of the rope are equal
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The net force on any object in equilibrium is
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Zero
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The equilibrium rule applies to
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Vector Quantities
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The Net force acting on an insect falling downward at constant velocity is
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Zero
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The support force on a 30kg dog sleeping on the floor is
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300N
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Burl and Paul have a total weight of 1300N. The tensions in the supporting ropes that support their scaffold add to 1700N. The weight of the scaffold itself must be
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400N
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If you toss a coin straight upward in train that slows while the coin is in the air, the coin will land
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In front of you
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If you toss a coin straight upward in train that gains speed while the coin is in the air, the coin will land
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In back of you
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If you toss a coin straight upward while in a train moving at constant velocity, the coin will land
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As if you were at rest
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An 800N man stands at rest on two bathroom scales so that he weight is distributed evenly over both scales. The reading on each scale is
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400N
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Katelyn runs along the aisle of a train that moves at 8m/s. Her speed relative to an observer at rest on the ground is
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Either depending on her running direction
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The speedometer of an automobile reads
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Instantaneous speed
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While a car travels around a circular tract at a constant speed its
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Not inertia is zero Not velocity is zero Not acceleration is zero None of the above
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A cart maintains a constant velocity of 100 m/s for 10 seconds, During this interval its acceleration is
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Zero
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A cart changes its speed from 90 m/s to 100 m/s in 10 seconds. During this interval its acceleration is
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100-90=10m/s2 and 10/10= 1m/s2
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What is the acceleration of a car that starts from rest and 5 seconds later reaches a speed of 20 m/s
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20m/s divided 5 = 4m/s2
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As water drops fall at a steady rate from a leaking faucet they
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Get father apart
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Which of the following is not a victor quantity
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Speed
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A bullet is dropped into a river from a very high bridge at the same time as another bullet is fired straight downward from a rifle. Neglecting air resistance, the acceleration just before striking the water is
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The same for each bullet
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Phil standing a the edge of a cliff throws a ball straight up and another ball straight down, both with the same speed. Neglecting air resistance, which ball hits the ground below with the greater speed
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Neither, both hit with the same speed
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An object falls freely from rest on a planet where the acceleration due to gravity is 20 m/s2. After 5seconds, the object will have a speed of
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20m/s2 * 5seconds = 100m/s
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If you throw a ball straight downward (in the absence of air resistance), after leaving your hand its acceleration is
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10m/s2
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If a freely falling object were equipped with speedometer, its speed reading would increase each second by about
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10m/s
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If an object falling freely were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be
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Greater than the second before
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The gain in speed each second for a freely falling object is about
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10m/s
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When a rocket shop accelerating in outer space runs out of fuel it
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no longer accelerates
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Whirl a rock at the end of a string on an ice covered pond and it follows a circular path if the string breaks, the tendency of the rock is to
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follow a straight line path
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If no external force are acting on a moving object it will
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continue moving at the same velocity
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A moving body must undergo a change in
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position
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Twelve seconds after starting from rest, an object falling freely will have a speed of
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more than 100 m/s (12 * 10 = 1200)
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A heavy object and a light object are dropped at the same time from rest in a vacuum. The heavier object reaches the ground
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at the same time as the lighter object
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A car maintains a constant velocity of 100km/hr for 10 seconds. During this interval it acceleration is
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Zero
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At one instant a heavy object in air is moving upward at 50 meters per second. One second later its speed in meters per second is approximately
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40m/s
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A ball tossed vertically upward rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always
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Directed downward
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While an object near the earth's surface is in free fall, its
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Velocity increases
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At one instant an object in free fall is moving downward at 50 meters per second. One second lather its speed should be about
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60m/s
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If an object movers with constant acceleration its velocity must
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Change by the same amount each second
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When a rock thrown straight upwards gets to the exact top of its path its
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Velocity is zero and its acceleration is about 10m/s^2
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It takes 6 seconds for a stone to fall to the bottom of a mine shaft. How deep is the shaft
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about 180m
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Distance is to displacement as
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Speed is to velocity
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An object falls freely from rest on a planet where the acceleration due to gravity is 20m/s^2. After 5 seconds, the object will have a speed of
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100m/s (20 * 5 =100)
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Ten seconds after starting from rest, a car is moving at 40m/s. What is the car's acceleration in meters per second per second
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4.0 (40 divided by 10 = 4)
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The scientist to first introduce the concept of inertia was
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Galileo
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compared with a 1kg block of solid iron, a 2kg block of solid iron has twice as much
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Inertia Mass Volume
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One object that has twice as much mass as another object also has twice as much
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Inertia
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A kilogram is a measure of an object's
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Mass
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Whereas Aristotle relied on logic in explaining nature, Galileo relied on
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Experiment
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An object in mechanical equilibrium is an object
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At rest Moving with constant velocity Having no acceleration All of these
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The force of friction on a sliding object is 10N. The applied force needed to maintain a constant velocity is
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10N
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An object is pulled northward with a force of 10N and southward with a force of 15 N. The Magnitude of the net force on the object is
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5N (15-10=5)
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Whenever the net force on an object is zero, its acceleration
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Is Zero
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What is the average speed of a car that travels 34.6 meters in 4.2 seconds
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8.2 (34.6 divided by 4.2 = 8.2)
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What is the acceleration rate of a car that speeds up from rest to 22.9m/s in 4.8s
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4.8 (22.9 divided by 4.8 =4.8)
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Inertia is defined as a
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Property of matter
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If no external forces act on a moving object, it will
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Continue moving at the same speed
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A hockey puck sliding across the ice finally comes to rest because
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Of friction
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When no forces act on moving objects their paths are normally
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Straight lines
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Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the Rock is to
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Follow a straight line path
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Which concept is being illustrated when a tablecloth is quickly yanked beneath dishes resting on a table?
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Inertia
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A package falls off a truck that is moving at 30 m/s . Neglecting air resistance, the horizontal speed of the package just before it hits the ground is
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About 30 m/s
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When a rocket ship gaining speed in outer space runs out of fuel it
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No longer gains speed
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A moving van with a stone lightly glued to the midpoint of its ceiling smoothly moves at constant velocity. She the glue gives way, the stone falls and hits the floor
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Exactly below the midpoint of the ceiling
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While you are standing in the aisle of a bus, the driver suddenly makes a left turn. You lurch to bathe right due to
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Your tendency to keep moving forward
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Nellie pulls with a force of 50 N on a horizontal rope tied to a tree at rest. The net force on the rope is
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Zero and rope tension is 50 N
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When you quickly jerk a cart forward that has a ball resting in the middle, the
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The back of the cart hits the ball
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A force is a vector quantity because it has both
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Magnitude and direction
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A block pulled to the left with 15 N and to the right with 5 N at the same time experiences a net force of
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10 N
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A tree stump is pulled northward by a 10-N force at the same time a 25-N force pulls it southward. The resistance force has a magnitude of
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15 N
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When a pair of 10-N forces act on a box of candy, the net force on the box is
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Zero, about 14 N, 20 N. Any of these depending on the directions of the forces
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When Nellie Newton hangs by the ends of a rope draped over a large pulley, the tension in each supporting vertical strand is
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Half her weight
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If Nellie hangs from a horizontal bar that is supported by four vertical ropes, the tension in the ropes
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Are each equal half her weight
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Suspend your body from a pair of vertical ropes and the tension in each rope will be
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Equal your weight
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Suspend your body from a pair of ropes slightly angled from the vertical and the tension in each rope will be
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Greater than half your weight
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When Nellie Newton hangs at rest in the middle of a clothesline, tension will be the same in each side of the rope when
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The angles for both sides of the rope are equal
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The net force on any object in equilibrium is
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Zero
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Burl and Paul paint signs together on a scaffold. Compared to their weights plus the weight of the scaffold, the sum of tensions in the supporting ropes is
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The same
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Burl and Paul have a total weight of 1300 N. The tensions in the supporting ropes that support their scaffold add to 1700 N. The weight of the scaffold itself must be
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400 N
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The net force acting on an insect falling downward at constant velocity is
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Zero
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The support force on a 10-N book at rest on a table is
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10 N
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Jason weighs 150 N and sits on his big brothers shoulders. Big brother weighs 400 N. The support force supplied by the floor must be
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550 N
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The support force on a 30-kg dog sleeping on the floor is
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300 N
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The force that causes earth to orbit the sun is due to gravity, while the force needed to keep earth moving as it circles the sun is
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No force at all
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If you toss a coin straight upward while In a train moving at constant velocity the coin will land
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As if you were at rest
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If you toss a coin straight upward in a train that gains speed while the coin is in the air, the coin will land
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In back of you
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Earth continually moves able it 30 km/s through space, which means the wall you stand next to also is moving at 30 km/s. When you jump vertically the wall doesn't slam into you because
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You're moving horizontally just as fast as the wall
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Experiments over philosophical discussions
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Science later greatly advanced when Galileo favored
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Velocity
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Which of the following is a vector quantity
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Your're moving horizontally just as fast as the wall
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Earth continually moves about 30 km/s through space, which means the wall you stand next to also is moving at 30 km/s. When you jump vertically the wall doesn't slam into you because
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Straight lines
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When no forces act on moving objects their paths are normally
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2
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The minimum number of forces that act on a bok resting on a table is
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Copernicus
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The first scientist to be credited for postulating that Earth circled the Sun was
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Keep rolling if friction is absent
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Galileo taught us that if you roll a ball along a level surface it will
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Add to equal her weight
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If Nellie hangs from a horizontal bar that is supported by four vertical ropes, the tension in the ropes
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In front of you
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If you toss a coin straight upwards in a train that slows while the coin is in the air, the coin will land
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Sags very little
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Monkey Mo hangs from the middle of a horizontal rope. Tension in the rope is greatest if the rope
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No adjustments
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A gymnast performing somersaults in a high-flying plane moving at constant velocity needs to make
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As if you were at rest
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If you toss a coin straight upward while in a train moving at constant velocity, the coin will land
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Vector quantities
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The equilibrium rule applies to
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A synthesis of a large body of well-tested knowledge
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A theory in the field of science is
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Galileo
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The first scientist to introduce the concept of inertia was
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Violent motion requires a sustained push or pull. The four elements are earth, water, air, and fire. All motion is either natural or violent. *All of the choices*
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The earliest and most influential Greek philosopher was Aristotle, who among many contributions taught that..
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14 N
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A pair of 10-N vectors at right angles to each other has a resultant of about
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Add up to equal your weight
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When you stand at rest on a pair of bathroom scales, the reading on each scale
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Exactly below the midpoint of the ceiling
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A moving van with a stone lightly glued to the midpoint of its ceiling smoothly moves at constant velocity. When the glue gives way, the stone falls and hits the floor
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10 N
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A block pulled to the left 15 N and to the right with 5 N at the same time experiences a net force of
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Physics
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The most basic of the sciences of physics, chemistry, and biology is
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About 30 m/s
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A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is
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Continue moving at the same speed
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If no external forces act on a moving object, it will
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All three involve different domains
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Science, art, and religion normally need not contradict one another because
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Zero and rope tension is 50 N
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Nellie pulls with a force of 50 N on a horizontal rope ties to a tree at rest. The net force on the rope is
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Follow a straight-line path
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Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the tendency of the rock is to
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400 N
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Burl and Paul have a total weight of 1300 N. The tensions in the supporting ropes that support their scaffold add to 1700 N. The weight of the scaffold itself must be
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Parrallel
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A parallelogram is a four-sided figure with opposite sides that are
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Magnitude and direction
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A force is a vector quantity because it has both
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Conclusively one way or the other
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For a scientific hypothesis to be valid, there must be a test for proving it
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550 N
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Jason weighs 150 N and sits on his big brother's shoulders. Big brother weighs 400 N. The support force supplied by the floor must be
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Of friction
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A hockey puck sliding across ice finally comes to rest because
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Inertia
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If your automobile runs out of fuel while driving, the engine stops.
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In equilibrium
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A hockey puck sliding at constant velocity across the ice is
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10 N
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The support force on a 10-N book at rest on a table is
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10 N
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The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant velocity is
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Your tendency to keep moving
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While you are standing in the aisle of a bus, the driver suddenly makes a left turn. You lurch to the right due to
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No longer gains speed
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When a rocket ship gaining speed in outer space runs out of fuel, it
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50 N
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The resultant of a 40-N force at right angles to a 30-N force is
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Hypothesis
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An educated scientific guess is a
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Back of the cart hits the ball
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When you quickly jerk a cart forward that has a ball resting in the middle, the
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No different
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Weigh yourself on a weighing scale and the scale shows your normal weight. If you carefully stand on tiptoes, the scale reading will be
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In back of you
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If you toss a coin straight upward in a train that gains speed while the coin is in the air, the coin will land
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Gaining, organizing, and applying new knowledge
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The scientific method is most effective in
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15 N
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A tree stump is pulled northward by a 10-N force at the same time a 25-N force pulls it southward. The resultant force has a magnitude of
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Be equal
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If Burl carries Paul piggy-back while standing in the /middle/ of a scaffold, the tensions in the two supporting ropes would
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Objects or systems at rest. Objects or systems in uniform motion in a straight line. *Both of these*
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The equilibrium rule, EF = 0, applies to
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Not vertical
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A pair of wires support a heavy painting. Tensions in the wires is great when they are
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The same
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Burl and Paul paint signs together on a scaffold. Compared to their weights plus the weight of the scaffold, the sum of tensions in the supporting ropes is
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Zero
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The net force on a any object in equilibrium is
