Newton's Third Law

Newton's Third Law

by Elizabeth Ache

Multiple Choice

A minivan read ends a motorcycle that was stopped at a red light, pushing it north into the intersection.

What is the action force in this scenario?

• The driver forgetting to stop for the light.

• The force of the minivan pushing the motorcycle as they collide.

• The fact that the motorcycle ended up in the middle of the interaction.

• The force of gravity pulling the minivan into the ground.

Multiple Choice

A minivan read ends a motorcycle that was stopped at a red light, pushing it north into the intersection.

What is the reaction force in this scenario?

• The force of the motorcycle pushing back on the minivan as they collide.

• The fact that the rider ended up in the hospital with whiplash.

• The fact that the motorcycle ended up in the middle of the interaction.

• The force of gravity pulling the minivan into the ground.

Multiple Choice

How does the action force (the amount of force the minivan applied to the motorcycle) compare to the reaction force (the amount of force the motorcycle applied to the minivan) during the collision?

• The action and reaction forces are equal.

  The minivan pushed the motorcycle with the same amount of force it experiences.

• The action force is larger than the reaction force.

  The minivan pushes the motorcycle harder.

• The reaction force is larger than the action force.

  The motorcycle pushes the minivan harder.

• There is not enough information to determine.

Multiple Choice

You accidentally hit your thumb while hammering.

What is the action force?

• The hammer hits your thumb.

• Your thumb hits the hammer.

• You thumb is broken.

• Your arm raises and lowers the hammer.

Multiple Choice

You accidentally hit your thumb while hammering.

What is the reaction force?

• The hammer hits your thumb.

• Your thumb hits the hammer.

• You thumb is broken.

• Your arm raises and lowers the hammer.

Multiple Choice

A fly is struck by a moving taxi cab.

How does the force felt by the fly compare to the force the windshield is struck with?

• The taxi hits the fly harde.

• The fly hits the taxi's windshield harder.

• The forces are equal.

• There is not enough information to determine.

Gun recoil is an example of Newton's Third Law.

Action Force:

The gun pushes the bullet forward.

​

​Reaction Force:

The bullet pushes the gun backwards.

Multiple Choice

When a gun fires a bullet: the bullet is accelerated forward and the gun is accelerated backwards (the recoil).

How do the forces compare?

• The force on the bullet is largest.

• The forces are equal.

• The force on the gun is largest. 

• Not enough information to determine. 

​The forces are equal, but...

Multiple Choice

When a gun fires a bullet: the bullet is accelerated forward and the gun is accelerated backwards (the recoil).

How do their accelerations compare?

• The acceleration of the bullet is largest.

• The accelerations are equal.

• The acceleration of the gun is largest. 

• Not enough information to determine. 

​Differences in mass cause differences in acceleration.

Multiple Select

Which of the following are examples of using Newton's Third Law?

• Swimming

• Canoeing

• Helicopter Lift

• Doing Pushups