Force Review 2

An example of an action / reaction force is

• the upward movement of a balloon after the air has been released
• the recoil of a gun after the bullet has been fired
• leaning against a stationary wall
• all of the answers

Friction acts

• only on moving objects.
• only between objects that are touching.
• only on stationary objects.
• between all objects in the universe.

What is the net force acting on the box shown in the picture?

• 30 N to the left
• 10 N down
• 10 N up
• 30 N to the right

An object's motion changes

• only if the object is at rest when a force acts upon it.
• only when a nonzero net force is applied to the object.
• when the forces acting on the object remain balanced.
• all of these

Which statement is true about gravitational forces?

• Only large masses exert a gravitational force on small masses.
  
• Only masses of equal size exert a gravitational force on each other.
• Every mass exerts a gravitational force on every other mass.
• Only moving masses exert a gravitational force on stationary masses.
  

Tom stops his car suddenly, which makes his lunch fly forward off the passenger seat. The lunch did not stop at the same time as the car because

• more force is required to stop softer objects than to stop harder objects.
• only objects touching the Earth's surface can be acted upon by an outside force.
• objects in motion can only be stopped by the application of a balanced force.
• objects in motion tend to stay in motion unless acted upon by an outside force

Imagine each person in the image drops an apple. How many of the apples would fall to the earth?

• All of the apples will fall to the Earth.
  
• Only the top person's apple.
• Only the top 3 people's apples.
• Only the top 5 people's apples.

Which of Newton’s laws makes a tennis ball fly in the opposite direction when hit with a tennis racket?

• 1st law because the ball remained at a constant velocity until it was acted on by an unbalanced force (the racket)
• 2nd law because the racket is accelerating to apply a force on the ball
• 3rd law because the racket and the ball apply equal and opposite forces on each other as they strike each other
• All of the Answers

What is a force?

• A force is equivalent to work.
  
• A force is a form of energy.
• A force is a substance that reacts with matter.
  
• A force is a push or a pull.

Suppose a bicycle was coasting on a level surface, and there was no friction. What would happen to the bicycle's speed?

• The speed would decrease until you finally came to a stop.
• The speed would decrease but you would never stop.
• The speed would increase since there is no friction.
• The speed would remain constant.