# 8th grade Science MOTION AND FORCE STUDY GUIDE Ken Ericksen
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to describe velocity you need to know

speed and direction
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according to Newton’s second law of motion

an object acted on by a force will accelerate in the direction of the force; F=m*a
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the distance traveled divided by the time taken to travel the distance is

speed
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the statement \”for every action, there is an equal but opposite reaction\” is a statement of

Newton’s 3rd Law
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inertia is

the tendency of an object to resist a change in motion and is dependent on the mass of the object
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acceleration is a change in

speed or direction. either speed up, slow down, or change direction
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momentum is a measure of

how hard it is to stop an object; momentum=m*v
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whenever a body is in motion

there is always friction to oppose the motion
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if gravity did not affect the path of a horizontally thrown ball, the ball would

continue in a straight path until acted on by another force
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the force you have to overcome to start an object moving is

static friction
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when you graph the motion of an object

you put time on the horizontal axis and distance on the vertical axis
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a feather falls through the air more slowly than a brick because of

air resistance
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Newton’s first law of motion states that an object remains at rest unless

an unbalanced force acts on it
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forces that are equal in size but opposite in direction are

balanced
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air resistance increases

as you move faster
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acceleration involves a change in

velocity
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the relationship among force, mass, and acceleration is stated in

Newton’s 2nd law
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speed is the rate of change in

distance
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distance

is a length traveled
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displacement

is the difference between start and end points and direction
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speed

is the distance traveled divided by the time taken to travel that distance
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velocity

is speed and direction of an object
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positive acceleration