PhysicsLand: Hot Air Balloon Races

When a cannon fires a cannonball we observe Newton's third law. Which force is the reaction force?

• The cannon moving forward

• The cannonball moving forward

• The cannon moving backward

• The cannonball moving backward

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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

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NGSS.MS-PS2-1

A person steps out of the boat and onto the dock.  As the person moves forward onto the dock, the boat moves backward.  Which statement best describes the backward motion of the boat as the person steps forward?

• For every action there is an equal and opposite reaction.
• Every mass exerts a force on every other mass.
• An object at rest tends to stay at rest.
• Friction opposes the motion of an object.

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What law of motion does this picture represent?

• Law of Inertia

• None of these above

• Law of Action and Reaction

• Law of Mass and Acceleration

Relating to Newton’s Third Law, action and reaction, what is the reaction when a rocket expels gas, smoke and flames from the nozzle end of the rocket engine?

• Nothing
• Propels in the opposite direction
• Creates a balanced force
• Creates friction

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NGSS.MS-PS2-1

How does the paddling motion of a swimmer help the swimmer move forward?

• As the swimmer's hands push the water backward, the water pushes forward on the swimmer.

• As the swimmer’s hands push the water backward, a current of water comes from behind and propels the swimmer.

• As the swimmer’s hands push the water backward, the water moves out of the way and lets the swimmer continue through the water

• As the swimmer’s hands push the water backward, the water keeps the swimmer floating.

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Which statement best explains why it hurts to punch a wall:

• When your fist hits the wall, the wall is solid so it hurts your hand.

• When your fist hits the wall, the wall exerts an equal force back onto your fist.

• When your fist hits the wall, your bones all smash together.

• When your fist hits the wall, the wall vibrates.

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NGSS.MS-PS2-1

When you blow up a balloon and let it go, it flies around the room. What are the action/reaction pairs?

• Action: balloon moving forward. Reaction: air coming out of the back of the balloon.

• Action: balloon moving forward. Reaction: friction with the air molecules.

• Action:air coming out of the back of the balloon.Reaction: balloon moving forward.

• Action: friction with the air molecules. Reaction: balloon moving forward.

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