Question 1

When you push against a wall, what is the force that the wall exerts on you called?

Accepted Answer

Reaction force (according to Newton's third law)

Question 2

A boxer cannot exert much force on a piece of tissue paper suspended in air because:

Accepted Answer

The tissue paper has too little mass to exert much force on the boxer's fist (therefore the opposite forces are very small)

Question 3

Which of the following best describes an action/reaction pair of forces according to Newton's third law?

Accepted Answer

They are always equal in magnitude and opposite in direction

Question 4

Suppose you are holding a magnet above a steel washer. As you move the magnet closer, the washer jumps up to the magnet. What is the force that the washer exerts on the magnet?

Accepted Answer

It exerts a force equal in magnitude and opposite in direction to the force the magnet exerts on the washer

Question 5

A rocket is propelled forward by:

Accepted Answer

The expulsion of exhaust gases backward, and the exhaust gases push the rocket forward

Question 6

When a tennis racket strikes a tennis ball, which statement is true about the forces involved?

Accepted Answer

The force on the ball and the force on the racket are equal in magnitude and opposite in direction

Question 7

A small insect hits your windshield while you are driving on the highway. How do the magnitudes of the forces compare?

Accepted Answer

The forces are equal in magnitude but opposite in direction

Question 8

When a bullet is fired from a rifle, which travels farther in the same time: the bullet or the rifle, and why?

Accepted Answer

The bullet, because it has a greater magnitude of acceleration

Question 9

Which of the following is the correct free-body diagram for an apple falling through the air?

Accepted Answer

A downward force of gravity from Earth and an upward force of air resistance

Question 10

A crate rests on the floor. You push on the crate, but it does not move. Which of the following best describes the forces acting on the crate?

Accepted Answer

The force you exert is balanced by the frictional force from the floor

Question 11

If two objects of dramatically different masses (such as a bus and a mosquito) collide head-on, what can be said about the forces they exert on each other?

Accepted Answer

They exert equal magnitude forces on each other

Question 12

A monkey dangles by a rope and pulls on his cage. What are the directions of the force vectors for the rope and the cage?

Accepted Answer

Each normally at right angles to each other

Question 13

What is the x-component of the force of gravity acting on an object on an incline, if the incline makes an angle $$	heta$$ with the horizontal?

Accepted Answer

$$mg \sin 	heta$$

Question 14

At the maximum height of a projectile launched vertically, what are the velocity and acceleration vectors?

Accepted Answer

Velocity is zero and acceleration points down

Question 15

Which of Newton's laws focuses on interactions between objects?

Accepted Answer

Newton's third law

Question 16

A 7 N weight is suspended by a rope that makes a 45° angle with the vertical. What is the vertical component of the tension in the rope?

Accepted Answer

$$7 \div \sqrt{2}$$

Question 17

Which of the following best describes the net force on a cart if the only horizontal force acting is from the surrounding air?

Accepted Answer

The net force is zero

Question 18

If you pull up on Earth with the same amount of force as Earth pulls down on you, why don't you move the Earth?

Accepted Answer

Because the mass of the Earth is so much greater, its acceleration is negligible

Question 19

Which of the following is NOT a correct statement of Newton's third law?

Accepted Answer

Action and reaction forces act on the same object

Question 20

A person stands on a scale in an elevator that is accelerating upward. How does the reading on the scale compare to the person's weight?

Accepted Answer

The reading is greater than the person's weight

Newton's Laws of Motion and Forces: Study Guide with Applications

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