The Third Law of Motion

Newton's Third Law States...

• Objects in motion stay in motion and objects at rest stay at rest
• Force is equal to mass times acceleration
• For each action there is an equal and opposite reaction

A baseball player bats a ball with a force of 1,000 N. The ball exerts a reaction force (without any additional forces action on it) against the bat of...

• Less than 1, 000 N
• 1,000 N
• More than 1,000 N

According to Newton's Third law the strength or magnitude of forces will be...

• smaller
• equal
• larger

Which force produces a change in motion?

• unbalanced force
• balanced force
• gravitational force
• frictional force

Forces do not occur in pairs.

• True
• False

Which best explains why we are able to accelerate forward when starting to run?

• As one leg moves backward, it provides an equal and opposite force for the other foot to move forward.
• No acceleration takes place. Runners are always at a fixed velocity.
• The striking foot pushes backward against the ground. The friction with the ground provides an equal and opposite force forward.
• The runner's upper body quickly leans forward, causing the entire body to begin accelerating forward

Action-reaction forces must act on the same object.

• True

• False

The nozzle of a rocket is pointed downward so that as fuel is ignited, the exhaust pushes downward. Why is this arrangement necessary for a rocket to function properly?

• The rocket is protected from the heat of the exhaust

• Burned fuel can be collected on the ground

• As fuel is combusted, the rocket pushes the gases backward and the gases push the rocket forward

• This allows the rocket to be steered properly

A bowling ball (5 kg) smashes into a bowling pin (1 kg). Which experiences the greater acceleration?

• They experience equal acceleration because their forces are equal but opposite

• The bowling ball experiences greater acceleration because it has a larger mass.

• The bowling pin experiences greater acceleration because it has a smaller mass.

When bouncing a ball with 10 N of force on the ground, does the ground move?

• Yes, because the ball and the ground experience equal but opposite force.

• No, even though the ball and the ground experience equal but opposite force.

• Yes, because the mass of the ground is much larger than the mass of the ball.