# 8th science forces and motion Patricia Smith
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When two forces act in the same direction

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inertia

the tendency of an object to resist change in its motion is known as
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the greater the mass of an boject

the greater its inertia
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weight

the force of gravity on a person or object on the surface of a planet is called
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one way to increase acceleration is by

decreasing mass
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friction

is the force that one surface exerts on another when the two rub against each other
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which of the following is an example of rolling friction

bike tires on the road as you ride
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friction

air resistence ia a type of
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the law of universal gravitation states that any two objects in the universe, without exception

attract each other
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forces can be added together only it they are

acting on the same object
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according to the law of conservation of momentum, when two objects collide in the avsence of friction

momentum is not lost
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the achievement of lifting a rocket off the ground and into space can be explained by

Newton’s third law
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force

in physical science, a push or a pull is called this
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velocity

the momentum of an object is in the same direction as its
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mass

the amount of matter in an object is called
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gravity

the force that pulls falling objects towards Earth is called
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According to Newton’s third law of motion, when a hammer strikes and exerts force on a nail, the nail

excerts an equal force back on the hammer
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newton

the SI unit for force is the
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balanced forces acting on an object

never change the object’s motion
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When an object’s distance from another object is changing

ia is in motion
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meter

the basic SI unit of length is
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time

Speed equals distance divided by
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When you know both the speed and direction of an object’s motion, you know the

velocity of the object
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time

you can show the motion of an object on a line graph in which you plot distance against
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rise

te steepness of a line on a graph is called
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Which is an example of deceleration

a car approaching a red light
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time

to determin the acceleration reat of an object, you must calculate the change in speed during each unit of
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kilometers per hour per hour

if speed is measured in likometers per hour and time is measured in hours, the unit of acceleration is
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average speed is

the total distance traveled divided by by the total time
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a reference point

a place or object used for comparision to determine if something is in motion is
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on a graph showing distance versus time, a horizonal line represents an object that is

not moving at all
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If you know the distance an object has traveled in a certain amount of time, you can determine

the speed of the object
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acceleration

changing direction is an example of a kind of
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15 km/h

if a bicyclist travels 30 kilometers in two hours, her average speed is
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the moon accelerates because it is

continuosly changing directions
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average speed

If you know a car traveled 30 kilometers in 3 hours. you can find its….
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Balanced forces

do not change an object’s motion
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the property of matter that resists a change is notion is called

inertia
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friction depends on the types of surfaces involved and how

hard the surfaces push together
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masee and distance

affect the gravitational attraction between objects
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Newton’s third law of motion states that for every action there is an equal by opposite

reaction
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a unit of momentum is

kgrm’s
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Motion is measured relative to a

reference point
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a child riding on a merry-go-round is accelerating because

his direction is changing
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The SI unit of acceleration is

the meter per second per second
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The overall force on an object after all teh forces are added together is called

the net force
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Unbalanced forces action on an object produce a change in the

object’s motion
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a measure of an object’s mass

is a measure of the object’s inertia
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on newton

is the force required to accelerate 1 kilogram of mass at 1 meter per second per second
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A person traveling in a car that stops suddenly keeps moving forward due to

inertia
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the downward force acting on an object in free fall is the force of

gravity
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a projectile

is an object that is thrown
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at the distance between two objects decreases, teh gravitational force between them

increases
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According to Newton’s third law of motion

the strength of a reaction force is equal to the strength of the action force.
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If the action force of a bat striking a ball accelerates the ball in one direction,

the reaction force accelerates the bat in the opposite direction
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friction acts in a direction opposite

to an object’s direction of motion
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a change in an object’s position relative to a regerence point is called

motion
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the distance traveled by a moving object per unit if time is called

speed
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the basic SI unith of lenght is the

meter
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the statement that the motion of a hurrican is 20 kilometers per hour in an easterly direction is a description of the hurricane’s

velocity
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acceleration is the rate of change in

speed
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the motion of a car stopping at a traffic light is an example of

negative acceleration. also called deceleration
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the abbreviation of the unit acceleration is

m/s 2
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If a car is speeding up,

its initial speed is less than its final speed
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If a train traveling at 30 m/s brakes to a stop in 1 minute