any push or pull that causes an object to move, stop, or change directions
friction
force that opposes, or acts against, motion when two surfaces rub against each other
magnetism
the force of repulsion or attraction between poles of magnets
gravitation
force that pulls all objects in the universe toward one another
balanced forces
forces equal in size and opposite in direction
unbalanced forces
when one force is greater than its opposite force
acceleration
when an object starts to move, speeds up, slows down, stops, or changes direction
net force
combined forces
work
use of a force to move an object through a distance
power
amount of work done for each unit of time
machine
something that makes work seem easier by changing the size or direction of the force
position
an object's place, or location
speed
measure of the distance an object moves in a given amount of time
velocity
an object's speed in a particular direction
acceleration
any change in velocity
momentum
measure of how hard it is to slow down or stop an object
inertia
property of matter that keeps it moving in a straight line or keeps it at rest
Newton's first law of motion
an object at rest will stay at rest, and an object in motion will continue moving in a straight line at a constant speed until an outside force acts on it
Newton's second law of motion
an object's acceleration depends on the size and direction of the force acting on it and on the mass of the object
Newton's third law of motion
For every action, there is an equal and opposite reaction
orbit
the path one body in space takes as it revolves around another body
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