Question 1

A 5 kg box is pulled across a horizontal surface with a constant force of 20 N. If the coefficient of kinetic friction between the box and the surface is 0.2, what is the acceleration of the box? (Take $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$a = 1.2\ \mathrm{m/s^2$}$$

Question 2

Which of the following best describes Newton's Third Law of Motion?

Accepted Answer

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

Question 3

A 10 kg object is suspended by two ropes at equal angles from the ceiling. If the system is in equilibrium, what is the tension in each rope? (Assume $$g = 9.8\ \mathrm{m/s^2$}$$ and each rope makes a $$45^\circ$$ angle with the ceiling.)

Accepted Answer

$$T = 69.3\ \mathrm{N}$$

Question 4

Which of the following statements about mass and weight is correct?

Accepted Answer

Weight is the force due to gravity acting on a mass.

Question 5

A car of mass $$m$$ accelerates from rest under a constant net force $$F. $$Which equation correctly relates the acceleration $$a to $$the force and mass?

Accepted Answer

$$a = \frac{F}{m}$$

Question 6

A skydiver reaches terminal velocity when:

Accepted Answer

The force of gravity equals the force of air resistance.

Question 7

Which of the following is NOT a correct free-body diagram for a box at rest on a horizontal surface?

Accepted Answer

A diagram showing only the gravitational force acting downward.

Question 8

A 2 kg object is acted on by a net force of 8 N. What is its acceleration?

Accepted Answer

$$a = 4\ \mathrm{m/s^2$}$$

Question 9

Which of the following best explains why a passenger moves forward in a car crash (assuming no seatbelt)?

Accepted Answer

Newton's First Law: The passenger continues in motion due to inertia.

Question 10

A block slides down a frictionless incline at angle $$	heta. $$Which equation gives the acceleration of the block?

Accepted Answer

$$a = g \sin 	heta$$

Question 11

A 3 kg object is suspended from a spring scale in an elevator accelerating upward at $$2\ \mathrm{m/s^2$}. $$What does the scale read?

Accepted Answer

$$35.4\ \mathrm{N}$$

Question 12

Which of the following is a correct statement of Hooke's Law?

Accepted Answer

$$F = -kx$$

Question 13

A 4 kg object is moving in a circle of radius 2 m at a constant speed of 3 m/s. What is the magnitude of the net force acting on the object?

Accepted Answer

$$F = 18\ \mathrm{N}$$

Question 14

Which of the following best describes the relationship between force and acceleration according to Newton's Second Law?

Accepted Answer

Force is directly proportional to acceleration.

Question 15

A 10 kg box is at rest on a horizontal surface. The coefficient of static friction is 0.5. What is the minimum horizontal force required to start moving the box?

Accepted Answer

$$F = 98\ \mathrm{N}$$

Question 16

Which of the following is NOT a vector quantity?

Accepted Answer

Mass

Question 17

A 2 kg object is pushed with a force of 10 N across a surface with a frictional force of 4 N opposing the motion. What is the acceleration?

Accepted Answer

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

Question 18

Which of the following best explains why astronauts feel weightless in orbit?

Accepted Answer

They are in free fall, accelerating at the same rate as their spacecraft.

Question 19

A 5 kg object is acted on by two forces: 10 N to the right and 6 N to the left. What is the acceleration?

Accepted Answer

$$a = 0.8\ \mathrm{m/s^2$}$$

Question 20

Which of the following is the best example of Newton's Third Law in action?

Accepted Answer

A swimmer pushes water backward and moves forward.

Forces, Newton's Laws, and Applications: Study Guide

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