physics chapter 2 – Flashcards
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The auto in the sketch moves forward as the brakes are applied. A bystander says that during the interval of braking, the auto's velocity and acceleration are in opposite directions. Do you agree or disagree?
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Agree. Acceleration (slowing the car) is opposite to velocity (the direction the car is moving).
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A space probe in remote outer space continues moving
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even though no force acts on it.
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Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the rock tends to
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follow a straight-line path.
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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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A sheet of paper can be pulled from beneath a box of cereal without toppling it if the paper is jerked quickly. This best demonstrates that
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the box has inertia.
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When dishes remain on a table when you yank the tablecloth beneath them, you're demonstrating
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inertia
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A ball rests in the middle of a cart. When you quickly jerk the cart forward, the ball
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hits the back of the cart.
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When you step off a bus moving at 10 m/s, your horizontal speed when you meet the ground is
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about 10 m/s.
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A hockey puck slides across a frozen pond. If ice friction and air resistance are neglected, the force needed to keep the puck sliding at constant velocity is
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0 N.
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The net force on any object moving at constant velocity is
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zero
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Earth moves about 30 km/s relative to the Sun. When you jump upward in front of a wall, the wall doesn't slam into you at 30 km/s because the wall
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and you move at the same horizontal speed, before, during, and after your jump.
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Inside the interior of a truck that moves at constant velocity is a package that drops from the midpoint of the ceiling. The package hits the floor
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exactly below the midpoint of the ceiling.
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If you are carrying a heavy bag of groceries and bang your hand against the wall, the concept that best explains why you are hurt is
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inertia
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A roller coaster car at an amusement park carrying 1 passenger takes 3 min to make its ride from start to finish. Neglecting friction, a car with 5 passengers would take
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the same time
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Newton's second law directly involves
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acceleration
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The force required to maintain an object at a constant velocity in free space is equal to
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zero
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If the mass of an object does not change, a constant net force on the object produces constant
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acceleration
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A given net force propels an object along a straight-line path. If the net force were doubled, its acceleration would
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double
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A given net force propels an object along a straight-line path by a force. If the mass were doubled, its acceleration would
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be half
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If an object's mass decreases while a constant force acts on it, the acceleration
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increases
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A push on a 1-kg brick accelerates the brick. Neglecting friction, to equally accelerate a 10-kg brick requires the force to be
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10 times as much
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A 10-N block and a 1-N block lie on a horizontal frictionless table. To push them with equal acceleration, we would have to push with
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10 times as much force as the heavier block
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A car has a mass of 1000 kg and accelerates at 2 m/s2. What is the magnitude of the force exerted on the car?
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2000 N
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A tow truck exerts a force of 3000 N on a car that accelerates at 2 m/s2. The mass of the car must be
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1500 kg
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A force of 1 N accelerates a 1-kg mass at 1 m/s2. The acceleration of a 2-kg mass acted upon by a force of 2 N is
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the same
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A girl pulls on a 10-kg wagon with a constant force of 30 N. What is the wagon's acceleration?
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3.0 m/s^2
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A block is dragged at constant velocity across a level surface by a force of 6 N. What is the force of friction between the block and the surface?
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6N
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A commercial jet has a mass of 5,000 kg and the thrust of its engine is 10,000 N. The acceleration of the jet when taking off is
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2 m/s^2
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A jumbo jet has a mass of 100,000 kg. The thrust for each of its four engines is 50,000 N. The acceleration of the jet when taking off is
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2m/s2
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A 10-kg block is pushed across a friction-free horizontal surface with a horizontal force of 20 N. The acceleration of the block is
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2 m/s^2
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A 10-kg block is pushed across a horizontal surface with a horizontal force of 20 N against a friction force of 10 N. The acceleration of the block is
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1 m/s^2
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A 10-kg block is pushed across a horizontal surface with a horizontal force of 30 N against a friction force of 10 N. The acceleration of the block is
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2 m/s^2
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Suppose you're coasting in a car at 60 km/h and apply the brakes until you slow to 40 km/h. When you suddenly release the brake, the car tends to
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continue moving at 40 km/h in the absence of forces.
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A heavy block at rest is suspended by a vertical rope. When the block is accelerated upward by the rope, the rope tension
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increases
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A 10-kg brick and a 1-kg book are dropped in a vacuum. The force of gravity on the 10-kg brick is
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10 times as much force as the 1 kg block
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A heavy object and a light object in a vacuum are dropped at the same time from rest. The heavier object reaches the ground
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at the same time as the lighter object
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How many forces act on an upwardly tossed coin when it gets to the top of its path?
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one; the force due to gravity
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When you toss a coin straight up, it moves upward, turns around, and drops. During this time the acceleration of the coin is
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downward and constant
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After a ball tossed upward leaves your hand, the force of gravity on it
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remains constant
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A 10-N falling object encounters 4 N of air resistance. The net force on it is
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6N
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A 10-N falling object encounters 10 N of air resistance. The net force on it is
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0N
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A ball tossed vertically upward reaches its highest point and then falls back to its starting point. During this up-and-down motion the acceleration of the ball is always
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directed downward
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A rock is thrown vertically upward. At the top of its straight-line path, its velocity is
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0 m/s
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If an object falls with constant acceleration, the velocity of the object must
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continually change by the same amount each second
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An elephant and a feather fall from a tree through the air to the ground below. The force of air resistance is greater on the..
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elephant
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A 1-kg ball is thrown straight up at 10 m/s. Neglecting air resistance, the net force that acts on the ball when it is half way to the top of its path is
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10 N
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When an object falls through the air and gains velocity, the net force actually
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decreases
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The air resistance of falling is greatly affected by an object's frontal area and
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speed
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When a falling object has reached its terminal velocity, its acceleration is
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zero
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A falling object that has reached its terminal speed continues to gain
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neither
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Two objects of the same size but unequal weights are dropped from a tall tower. Taking air resistance into consideration, the object to hit the ground first will be the...
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heavier object
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A light woman and a heavy man jump from an airplane at the same time and open their same-size parachutes at the same time. Which person will get to a state of zero acceleration first?
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the light woman
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A skydiver who weighs 500 N reaches terminal velocity at 90 km/h. The air resistance on the skydiver is
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500 N
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A sack of potatoes weighing 200 N falls from an airplane. As the velocity of fall increases, air resistance also increases. When air resistance equals 200 N, the sack's acceleration is
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5 m/s^2
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A skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration
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decreases
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When a 500-N parachutist opens his chute and experiences 800 N of air resistance, the net force on him is
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300 N upward
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A ball is thrown vertically upward. Because of air resistance, its speed when returning to its starting level compared with its initial speed is
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less
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A pair of tennis balls fall through the air from a tall building. One ball is regular and the other is filled with lead pellets. The ball to reach the ground first is the
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lead filled ball
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A pair of tennis balls fall through the air from a tall building. One ball is regular and the other is filled with lead pellets. Air resistance just before they hit is actually greater for the
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led filled ball
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Action and reaction forces comprise the parts of
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a single interaction
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A player hits a ball with a bat. If one part of the interaction is the bat against the ball, the other part is the
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ball against the bat
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A karate chop breaks a board with a blow of 3000 N. The force that acts on the hand during this event is
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3000 N
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A person is attracted toward the center of Earth by a 500-N gravitational force. The force of attraction of Earth toward the person is
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500N
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When a baseball player hits a ball with a force of 1000 N, the ball exerts force on the bat of
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1000 N
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A car traveling at 100 km/h strikes an unfortunate bug that splatters on the windshield. The force of impact is greater on the
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same for both
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An archer shoots an arrow. If the action force is the bowstring on the arrow, the reaction is the
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arrows push on the bowstring
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A player catches a ball. Consider the action force to the ball against the player's glove. The reaction is the
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force of the glove on the ball
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As a ball falls, the action force is the pull of Earth's mass on the ball. The reaction force is the
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pull of the ball's mass on Earth
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Earth pulls on the Moon. Similarly the Moon pulls on Earth, evidence that
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they both pull on each other and are an action-reaction pair
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A Mack truck and a Mini Cooper traveling at the same speed collide head-on. The collision force is greatest on the
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same
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A Mack truck and a Mini Cooper traveling at the same speed collide head-on. The vehicle to undergo the greatest change in velocity will be the
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mini cooper
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The force exerted on the tires of a car to directly accelerate it along a road is exerted by the
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road
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You toss a ball upward where air resistance is negligible. After the ball leaves your hand the force on it
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is the single force due to gravity, always directed downward.
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Arnold Strongman and Suzie Small each pull on opposite ends of a rope in a tug-of-war. The greatest force on the rope is exerted by
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same
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Arnold Strongman and Suzie Small have a tug-of-war on a polished floor. Arnold wears socks and Suzie wears gym shoes. The likely winner is
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Suzie
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Both ends of a piece of rope are pulled by two people in a tug-of-war. If each pulls with a 400-N force, the tension in the rope is
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400 N
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Two people, one twice as massive as the other, attempt a tug-of-war with 12 m of rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of
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4 M
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A friend says that the heavyweight champion of the world cannot exert a force of 50 N on a piece of tissue paper with his best punch. The tissue paper is held in midair, no wall, no tricks. You
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agree that it can't be done
