Q: Which of the following best describes Newton’s third law of motion?

$$\text{Whenever two objects interact, they exert on each other forces that are equal in magnitude but opposite in direction.}$$

Q: A book rests on a table. Which of the following forces are an interaction pair?

$$\text{The gravitational force exerted by Earth on the book and the gravitational force exerted by the book on Earth}$$

Q: A 1.2 kg book is placed on a spring with a spring constant $$k = 5.0 \times 10^3$\ \text{N/m}. $$What is the displacement of the spring from its relaxed position when the book is at rest?

$$2.4 \times 10$$^{-3}$$\ \text{m}$$

Q: Which of the following is a field force?

$$\text{The gravitational force exerted by Earth on a ball}$$

Q: A person stands in an elevator accelerating upward. The forces acting on the person are:

$$\text{An upward contact force from the floor and a downward gravitational force from Earth}$$

Q: A feather and a brick are falling freely in an evacuated tube. Which statement is correct?

$$\text{The gravitational force on the feather is smaller than on the brick}$$

Q: Which of the following is NOT a characteristic of an interaction pair (Newton’s third law)?

$$\text{The forces act on the same object}$$

Q: A block is at rest on a shelf, and a second block rests on top of the first. Which objects are in the environment of the bottom block?

$$\text{The shelf, the top block, and Earth}$$

Q: Which of the following best describes translational equilibrium?

$$\text{The vector sum of the forces exerted on the object is zero}$$

Q: The SI unit of force, the newton (N), is defined as:

$$1\ \text{N} = 1\ \text{kg} \cdot \text{m}/\text{s}^2$$

Question 1

A car is traveling down a straight highway at a constant speed of 100 km/h. What is the vector sum of the forces exerted on the car?

Accepted Answer

$$0$$

Question 2

Which of the following best describes Newton’s third law of motion?

Accepted Answer

$$	ext{Whenever two objects interact, they exert on each other forces that are equal in magnitude but opposite in direction.}$$

Question 3

A book rests on a table. Which of the following forces are an interaction pair?

Accepted Answer

$$	ext{The gravitational force exerted by Earth on the book and the gravitational force exerted by the book on Earth}$$

Question 4

A 1.2 kg book is placed on a spring with a spring constant $$k = 5.0 	imes 10^3$\ 	ext{N/m}. $$What is the displacement of the spring from its relaxed position when the book is at rest?

Accepted Answer

$$2.4 	imes 10$$^{-3}$$\ 	ext{m}$$

Question 5

Which of the following is a field force?

Accepted Answer

$$	ext{The gravitational force exerted by Earth on a ball}$$

Question 6

A constant force $$F is $$exerted on a cart of mass $$m$$ initially at rest for a time interval $$\Delta t. $$What is the change in momentum of the cart?

Accepted Answer

$$F \Delta t$$

Question 7

If you exert a force of 200 N on a friend on roller skates and she starts from rest, how far does she move in 2.0 seconds if her mass is 50 kg?

Accepted Answer

$$16\ 	ext{m}$$

Question 8

A person stands in an elevator accelerating upward. The forces acting on the person are:

Accepted Answer

$$	ext{An upward contact force from the floor and a downward gravitational force from Earth}$$

Question 9

A spring is stretched by a distance $$x$$ from its relaxed position. According to Hooke’s law, what is the force exerted by the spring?

Accepted Answer

$$F = -kx$$

Question 10

Two people, A and B, pull on opposite ends of a rope at rest, each exerting a force $$F. $$What is the tension in the rope?

Accepted Answer

$$F$$

Question 11

A feather and a brick are falling freely in an evacuated tube. Which statement is correct?

Accepted Answer

$$	ext{The gravitational force on the feather is smaller than on the brick}$$

Question 12

Which of the following is NOT a characteristic of an interaction pair (Newton’s third law)?

Accepted Answer

$$	ext{The forces act on the same object}$$

Question 13

A block is at rest on a shelf, and a second block rests on top of the first. Which objects are in the environment of the bottom block?

Accepted Answer

$$	ext{The shelf, the top block, and Earth}$$

Question 14

A constant force is exerted for a short time interval on a cart initially at rest. If the mass of the cart is doubled, what happens to the final speed after the same force and time interval?

Accepted Answer

$$	ext{It is halved}$$

Question 15

Which of the following best describes translational equilibrium?

Accepted Answer

$$	ext{The vector sum of the forces exerted on the object is zero}$$

Question 16

The SI unit of force, the newton (N), is defined as:

Accepted Answer

$$1\ 	ext{N} = 1\ 	ext{kg} \cdot 	ext{m}/	ext{s}^2$$

Question 17

A tennis ball of mass $$0.20\ 	ext{kg} is $$hit by a racquet and experiences an upward acceleration of $$9g. $$What is the magnitude of the force exerted by the racquet on the ball?

Accepted Answer

$$20\ 	ext{N}$$

Chapter 8: Force – Principles and Practice of Physics (Mazur, 2nd Edition)

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