Rafi presses his palm against a wall, and the wall presses back. Which law explains these paired forces?

When do the two forces in an interaction occur?

Why can't an action-reaction pair balance the forces on one object?

A book rests on a table. Which two forces form an interaction pair?

Earth pulls a falling book downward. Which force is its interaction partner?

A student starts walking on a rough sidewalk. Which interaction supplies the external force that accelerates the student forward?

On an ideal surface with no friction, can a student start moving forward by ordinary walking?

A car accelerates as its driven tires grip the road. Which interaction supplies the external force that accelerates the whole car?

Liza steps from a small boat toward a dock. With water resistance neglected, how does her push affect the boat?

A rocket fires its engine in a vacuum. Which statement correctly explains whether its speed can change?

In the balloon-jet activity, which two objects exert the forces that propel the jet?

A balloon-powered car must travel toward the school gate. Which way should its air outlet point?

The hooked instruments are pulled from opposite ends. What force does each instrument measure?

A light trolley and a heavy trolley are released by a compressed spring between them. Ignoring friction, why does the light trolley gain speed faster?

What is a system in a motion investigation?

Ana treats two trolleys and the spring between them as one system. How are the spring's pushes on the trolleys classified?

For a system containing only two trolleys, which force comes from outside its boundary?

A stationary toy car's fan blows into its attached sail. If the horizontal forces on the fan and sail exactly cancel, what happens when other horizontal forces are negligible?

The diagram shows the mutual pushes between carts A and B. Which arrow belongs in a free-body diagram of A alone?

A moving cart pushes another cart. What determines whether the first cart speeds up, slows down, or changes direction?