Question 1

Which of the following best describes an inertial reference frame?

Accepted Answer

A reference frame at rest or moving at constant velocity relative to the ground.

Question 2

A car suddenly stops and you feel yourself being 'thrown' forward. According to Newton's laws, what is actually happening?

Accepted Answer

The car is accelerating backward beneath you, and you continue moving forward due to inertia.

Question 3

A wrench floats 2 m forward inside a windowless spaceship in 10 seconds. What can you conclude?

Accepted Answer

The ship’s acceleration is in the -x direction.

Question 4

How can you calculate the ship’s acceleration from the observation that the wrench floats 2 m forward in 10 seconds?

Accepted Answer

Use a kinematic equation relating displacement, time, and acceleration.

Question 5

Given the wrench floats 2 m in 10 s, what is the ship’s acceleration?

Accepted Answer

$$a_x = -0.04\ \mathrm{m/s^2$}$$

Question 6

Which of the following is true for an object in static equilibrium?

Accepted Answer

The net force acting on the object is zero.

Question 7

A car is parked on a hill with slope $$	heta. $$What is the correct expression for the magnitude of the frictional force $$\vec{f}_s$$ acting on the car?

Accepted Answer

$$f_s = mg\sin	heta$$

Question 8

A skier of mass $$70\ \mathrm{kg} is $$pulled up a hill with a $$10^\circ$$ slope at constant speed. If friction is negligible, what is the tension in the rope?

Accepted Answer

$$T = mg\sin	heta$$

Question 9

Which is the correct equation for the y-direction forces on the skier pulled up a hill at constant speed?

Accepted Answer

$$n - mg\cos	heta = 0$$

Question 10

Which is the correct equation for the x-direction forces on the skier pulled up a hill at constant speed?

Accepted Answer

$$T - mg\sin	heta = 0$$

Question 11

If a rope is in static equilibrium and is pulling on a wall with a force of $$100\ \mathrm{N}$$, what force does the wall exert on the rope?

Accepted Answer

$$100\ \mathrm{N} in $$the opposite direction

Question 12

Boxes A and B are connected and accelerating to the right on a frictionless surface. Box B has a larger mass than box A. How do the two tensions $$T_1 ($$pulling both boxes) and $$T_2 ($$between the boxes) compare?

Accepted Answer

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

Question 13

Which of the following statements about tension in a rope is correct?

Accepted Answer

Tension pulls equally in both directions along the rope.

Question 14

A ring is pulled by three forces and remains at rest. If two forces are $$10\ \mathrm{N}$$ each at an angle $$	heta$$ from the horizontal, what must the magnitude of the third force $$F be to $$maintain equilibrium?

Accepted Answer

$$F = 20\cos	heta$$

Question 15

Which of the following is NOT a correct step in solving a Newton’s Second Law problem using a free-body diagram?

Accepted Answer

Add fictitious forces in inertial frames.

Question 16

A rope passes over a massless, frictionless pulley. If a $$10\ \mathrm{kg}$$ mass hangs on one side and a $$20\ \mathrm{kg}$$ mass on the other, what is the tension in the rope?

Accepted Answer

$$T = \frac{2m_1m_2g}{m_1$ + m_2$}$$

Question 17

Which of the following is a characteristic of dynamic equilibrium?

Accepted Answer

The object moves with constant velocity and the net force is zero.

Question 18

Why is it important to use an inertial reference frame when applying Newton’s Second Law?

Accepted Answer

Because only in inertial frames does $$\sum \vec{F} = m\vec{a}$$ hold true.

Question 19

A skier is pulled up a hill at constant speed. If the mass is $$m$$ and the slope is $$	heta$$, what is the normal force $$n$$ exerted by the hill?

Accepted Answer

$$n = mg\cos	heta$$

Newton’s Laws, Free-Body Diagrams, and Tension: Study Notes for Physics with Calculus

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