Question 1

A car with mass $$m = 1500\ \mathrm{kg} is $$being towed at a constant speed by a rope at an angle $$	heta = 20^\circ$$ above the horizontal. The friction force opposing the motion is $$f = 320\ \mathrm{N}. $$What is the tension $$T in $$the rope?

Accepted Answer

$$T = \dfrac{f}{\cos 	heta}$$

Question 2

A 46 g golf ball is putted with an initial speed of $$3.0\ \mathrm{m/s}$$ and experiences a friction force of $$0.020\ \mathrm{N}. $$What is the acceleration of the ball?

Accepted Answer

$$a = -\dfrac{f}{m}$$

Question 3

A skier slides down a $$27^\circ$$ frictionless slope. What is the skier’s acceleration?

Accepted Answer

$$a = g \sin 	heta$$

Question 4

Which of the following best describes the normal force acting on an object at rest on a horizontal surface?

Accepted Answer

It is perpendicular to the surface and equal in magnitude to the object's weight.

Question 5

A box is sitting on the floor of an elevator accelerating upward. Which statement is true about the normal force $$n on $$the box?

Accepted Answer

$$n \u003e mg$$

Question 6

The maximum static friction force between two surfaces is given by:

Accepted Answer

$$f_{s,\mathrm{max}} = \mu_s n$$

Question 7

A 70 kg astronaut weighs less on the Moon than on Earth because:

Accepted Answer

The acceleration due to gravity $$g is $$less on the Moon.

Question 8

A block is pushed gently and does not move. As the pushing force increases, what happens to the static friction force?

Accepted Answer

It increases up to a maximum value.

Question 9

Which equation correctly relates the net force and acceleration for an object of mass $$m$$?

Accepted Answer

$$\sum \vec{F} = m \vec{a}$$

Question 10

A block is sliding at constant speed across a horizontal surface. Which statement is true about the kinetic friction force?

Accepted Answer

It is equal in magnitude and opposite in direction to the applied force.

Question 11

A ball is dropped from rest and falls through air. As its speed increases, the drag force acting on it:

Accepted Answer

Increases in magnitude.

Question 12

Which of the following is true about the tension in a massless rope passing over a massless, frictionless pulley?

Accepted Answer

The tension is the same on both sides of the pulley.

Question 13

A 200 kg stage set is attached to a 100 kg stagehand by a massless rope over a frictionless pulley. When the rope is released, what is the acceleration of the stagehand?

Accepted Answer

$$a = \dfrac{m_S - m_M}{m_S + m_M} g$$

Question 14

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

Accepted Answer

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

Question 15

A block is pushed across a rough surface and comes to rest. Which force is responsible for stopping the block?

Accepted Answer

Kinetic friction

Question 16

A box is at rest on a horizontal table. If the table is suddenly accelerated upward, what happens to the normal force on the box?

Accepted Answer

It increases.

Question 17

Which of the following is the correct formula for the drag force on a sphere moving at high speed through air?

Accepted Answer

$$D = \dfrac{1}{2} C_D \rho A v^2$

Question 18

Two blocks, A and B, are in contact and pushed to the right on a frictionless surface. Block A has a larger mass than block B. How do the two tension forces compare?

Accepted Answer

$$T_2$$ \u003e $$T_1$$

Question 19

A person stands on a scale in an elevator accelerating downward. What does the scale read?

Accepted Answer

Less than the person’s true weight

Question 20

Which of the following is NOT a property of the normal force?

Accepted Answer

It is always parallel to the surface.

Applying Newton’s Laws: Equilibrium, Forces, and Dynamics

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