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force that pulls objects toward Earth

When you drop something, the force of gravity makes it fall downward.

kinetic energy

energy an object has because of its motion

As they ski down a steep ramp, ski jumpers gain kinetic energy.


force between two objects or surfaces that keeps the objects from moving freely

Friction is what stops a ball from rolling across rough grass.


the slowing force of air or another substance on a moving object

It’s hard to walk into a strong wind, because the fast-moving air creates extra drag on your body.


shaped in a way that makes it easier to move through the air

A sports car’s sleek shape makes it more aerodynamic.


upward force

Air flowing around an airplane’s wings creates the lift that makes the plane fly.

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