friction

the force that opposes motion between two surfaces that are touching

freefall

when the only force acting on an object is gravity; all objects near Earth fall at the SAME SPEED (regardless of how heavy/massive they are!!!)

equal and opposite forces

whenever a force is exerted, there is another force that is equal in size and opposite in direction

inertia

objects in motion tend to stay in the same motion; objects at rest tend to stay at rest

momentum

mass x speed

zero (momentum)

an object at rest has ______ momentum

SI Unit for force

N (Newton)

Gravity depends upon...

the masses of the two objects and the distance between them (more mass means more gravity, more distance means less gravity)

Weight on planets

Planet has more mass = planet has more gravity = things weigh more

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