2. A force is a push or pull that acts on an object.

3. When an object pulls or pushes another object, the first object is exerting a force on the second one.

4. Object 1 (the puppy) is pulling Object 2 (the girl’s hair).

5. Forces can make a moving object speed up, slow down, or change direction.

6. Forces have both magnitude and direction. Magnitude means the strength of the force.

7. Remember that force can be measured. Magnitude is measured in units called newtons(N).

8. Every object in the universe exerts a gravitational pull on every other object.

9. Everything that has mass has a gravitational pull. Right now, your desk's gravitational field is pulling on you, and your gravitational field is pulling on the desk. However, since gravity is a relatively weak force, unless you're an extremely large object like a planet, you can't feel this pull. We do, however, feel the pull of the Earth on us.massforce

10. Only an object that is really, really large like Earth is strong enough to be felt.

11. Earth’s gravity pulls other objects toward its center.

12. Every time you jump into the air, the Earth's gravitational field pulls you back down. If you use more force, you can jump higher, but you always return to the Earth.

13. An apple falls to the ground because the force of gravity pulls it toward Earth’s center.

14. Gravity causes the velocity of the apple to increase as it falls.

15. After one second of falling, an apple’s velocity will be about 10 meters per second 10 m s

16. After two seconds of falling, an apple’s velocity will be about 20 m downward. s

17. A pendulum swings because of the force of gravity. When the pendulum is released, gravity pulls on it and make it swing downward. Gravity makes the pendulum increase its speed as it swings downward. When the pendulum starts to swing upward, the force of gravity slows the pendulum until it stops. Then the pendulum is pulled downward again and it swings in the other direction.