# 8th grade Science MOTION AND FORCE STUDY GUIDE

to describe velocity you need to know
speed and direction
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
the distance traveled divided by the time taken to travel the distance is
speed
the statement “for every action, there is an equal but opposite reaction” is a statement of
Newton’s 3rd Law
inertia is
the tendency of an object to resist a change in motion and is dependent on the mass of the object
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
whenever a body is in motion
there is always friction to oppose the motion
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
the force you have to overcome to start an object moving is
static friction
when you graph the motion of an object
you put time on the horizontal axis and distance on the vertical axis
a feather falls through the air more slowly than a brick because of
air resistance
Newton’s first law of motion states that an object remains at rest unless
an unbalanced force acts on it
forces that are equal in size but opposite in direction are
balanced
air resistance increases
as you move faster
acceleration involves a change in
velocity
the relationship among force, mass, and acceleration is stated in
Newton’s 2nd law
speed is the rate of change in
distance
distance
is a length traveled
displacement
is the difference between start and end points and direction
speed
is the distance traveled divided by the time taken to travel that distance
velocity
is speed and direction of an object
positive acceleration
means that the object is getting faster over time, or speeding up
negative acceleration
means that the object is slowing down