Hewitt 5.3 hw

When hitting a tennis ball with your racquet, the force on the ball has the same magnitude as the force on the

• racquet, and in the same direction
• racquet
• hand that holds the racquet
• player

A Volkswagen Bug and a Volvo truck have a head-on collision. Which statement is true??

• Both forces are identical.
• The greater force acts on the Volvo truck.
• The magnitudes of both forces are the same.
• The greater force acts on the Volkswagen Bug.

Earth pulls down on you with a gravitational force that you call your weight. Do you pull up on Earth with the same amount of force?

• No, the contact force from the ground cancels the force by you on Earth.
• Earth exerts a much greater force on you than you exert on Earth.
• Yes, you pull up on Earth with the same force.
• No, the contact force from the ground cancels the force of Earth on you.

If the forces that act on a cannonball and the recoiling cannon from which it is fired are equal in magnitude, why do the cannonball and cannon have very different accelerations?

• The force from the cannon ball on the cannon produces little acceleration because it lasts for such a brief time.
• The cannon weighs so much that friction with the ground alone prevents it from accelerating.
• Remember F = ma, and note that the cannon has a much greater mass than the cannon ball, so the cannon accelerates less for the same force.
• The cannon pushes on the cannon ball with a much greater force than the cannon ball pushes on the cannon.

Identify the force that propels a rocket.

• The rocket is propelled by the reaction force of the exhaust gasses bouncing off the air molecules outside the rocket.
• The rocket is propelled because the action force of the rocket on the exhaust gases is greater than the reaction force of the exhaust gasses on the rocket.
• The rocket is propelled by the reaction force from the particles accelerated out the rear by an action force from the rocket.
• The rocket is propelled because the action force of the rocket on the exhaust gases is less than than the reaction force of the exhaust gasses on the rocket.

How does a helicopter get its lifting force?

• The helicopter exerts downward forces on the air that are slightly greater than the force of gravity, so it can hover.
• The helicopter exerts a downward force on Earth; the reaction force of Earth on the helicopter is called lift.
• The helicopter exerts downward forces on air; the reaction forces of the air on the helicopter are upward and called lift.
• The helicopter exerts upward forces on the air; the reaction forces of the air on the helicopter are downward and called lift.

Can you physically touch a person without that person touching you with the same amount of force?

• No, when you touch a person, they must touch you with an equal and opposite force.
• Yes, you can touch a person while they choose to not touch you back.
• Yes, when a heavier person touches a lighter person, the lighter person touches back with less force.
• Yes, when you touch a person, they touch you back with a force that is slightly less due to friction.