2.3 | Newton's Third Law

Newton's Third Law states:

For every action there is an equal reaction.

• True

• False

Is the following statement true or false, and why?

Forces on objects always occur in pairs.

• False, this does not happen in space.

• False. Gravity is an example where there is only on force.

• True, but the forces need to be unbalanced.

• True. If you push a box, the box pushes back just as hard.

A batter hits a baseball with a bat. What is the action-reaction pair?

• Bat hits ball. Ball hits bat.

• Pitcher throws ball. Batter hits ball.

• Hand throws ball. Bat his ball.

• Bat hits ball. Ball pushes through the air.

The Earth's gravity pulls on you. Do you pull on the Earth?

• No, people don't have gravity.

• Yes. Earth pulls me, I pull the Earth.

• Yes, but the size of the force is so small it can't be measured.

• No, the Earth has too much mass for any one person to pull.

What action-reaction pair explains how rockets move?

• Rocket burns fuel. Fuel pushes the ground.

• Rocket burns fuel. The rocket's weight gets smaller.

• Rocket pushes burning fuel. Burning fuel pushes rocket back.

• Rocket exhaust pushes the air. The air pushes the exhaust and rocket back.