Question 1

A 6-kg bucket is being pulled straight up by a string at a constant speed. What is the tension in the rope? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$T = 58.8\ \mathrm{N}$$

Question 2

A block of mass $$m is $$hanging at rest from a rope. Which of the following equations correctly describes the forces acting on the block?

Accepted Answer

$$T = m g$$

Question 3

A 15 kg box (A) is in contact with a 5 kg box (B) on a frictionless surface. A horizontal force of 100 N is applied to box A. What is the acceleration of the system?

Accepted Answer

$$a = 5\ \mathrm{m/s^2$}$$

Question 4

A toboggan slides down a frictionless hill inclined at angle $$\alpha. $$What is the acceleration of the toboggan?

Accepted Answer

$$a = g \sin \alpha$$

Question 5

Two blocks are connected by a string over an ideal pulley. Block A (on a $$30^\circ$$ incline) has mass $$m_A$$, and block B (hanging) has mass $$m_B. $$What is the acceleration of the system?

Accepted Answer

$$a = g \dfrac{m_B - m_A \sin 30^\circ}{m_A + m_B}$$

Question 6

A 4 kg block and a 6 kg block are connected by a massless rope and pulled with a force $$F on a $$frictionless surface. What is the tension $$T in $$the rope between them?

Accepted Answer

$$T = \dfrac{4}{10} F$$

Question 7

A mass $$m is $$falling freely under gravity. What is the net force acting on it?

Accepted Answer

$$F_{	ext{net}} = m g$$

Question 8

Which of the following best describes Newton’s Third Law?

Accepted Answer

For every action, there is an equal and opposite reaction.

Question 9

A person pushes backward on the ground while walking. According to Newton’s Third Law, what force propels the person forward?

Accepted Answer

The ground pushes forward on the person.

Question 10

A 6-kg bucket is pulled upward with an acceleration of $$3\ \mathrm{m/s^2$}. $$What is the tension in the rope?

Accepted Answer

$$T = 78\ \mathrm{N}$$

Question 11

In the Atwood machine, two masses $$M = 0.6\ \mathrm{kg}$$ and $$m = 0.4\ \mathrm{kg}$$ are connected by a string over a frictionless pulley. What is the acceleration of the system? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$a = 1.96\ \mathrm{m/s^2$}$$

Question 12

A box is at rest on a horizontal surface. Which of the following statements is true?

Accepted Answer

The normal force equals the weight of the box.

Question 13

A 15 kg box (A) is in contact with a 5 kg box (B) on a frictionless surface. A horizontal force of 100 N is applied to box A. What is the force exerted by box A on box B?

Accepted Answer

$$25\ \mathrm{N}$$

Question 14

A toboggan of mass $$m$$ slides down a frictionless incline at angle $$\alpha. $$What is the normal force exerted by the hill?

Accepted Answer

$$n = m g \cos \alpha$$

Question 15

Which of the following is NOT an action-reaction pair according to Newton’s Third Law?

Accepted Answer

The force of gravity and the normal force on a box at rest.

Question 16

A block of mass $$m is $$pulled upward with a downward acceleration $$a. $$What is the tension in the rope?

Accepted Answer

$$T = m (g - a)$$

Question 17

A person pulls a 10 kg box across a frictionless floor with a force of 50 N. What is the acceleration of the box?

Accepted Answer

$$a = 5\ \mathrm{m/s^2$}$$

Question 18

A 6-kg bucket is pulled upward with a downward acceleration of $$3\ \mathrm{m/s^2$}. $$What is the tension in the rope?

Accepted Answer

$$T = 40.8\ \mathrm{N}$$

Question 19

A block of mass $$m is at $$rest on a horizontal surface. Which equation correctly represents the equilibrium condition?

Accepted Answer

$$\sum F_y = 0$$

Newton’s Laws of Motion: Applications and Problem Solving

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