Q: A 4 kg object is pushed across a rough surface with a constant velocity. The coefficient of kinetic friction is 0.3. What is the magnitude of the frictional force?

$$F_{\text{friction}} = 11.76\ \text{N}$$

Q: A 6 kg object is acted upon by two forces: 20 N to the right and 8 N to the left. What is the acceleration of the object?

$$a = 2\ \text{m/s}^2$$\ \text{to the right}

Q: A 10 kg box is pulled with a force of 40 N along a horizontal surface. If the box accelerates at $$2\ \text{m/s}^2$$, what is the net force acting on the box?

$$F_{\text{net}} = 20\ \text{N}$$

Q: A person pushes a 5 kg box on a floor with a force of 25 N. The box does not move. What is the magnitude of the static friction force?

$$F_{\text{friction}} = 25\ \text{N}$$

Question 1

A 5 kg box is at rest on a horizontal table. Which of the following statements best describes the forces acting on the box?

Accepted Answer

The box experiences two equal and opposite forces: gravity downward and the normal force upward.

Question 2

A car accelerates from rest with a constant force. According to Newton’s second law, which equation correctly relates the net force $$F to $$the car’s mass $$m$$ and acceleration $$a$$?

Accepted Answer

$$F = m \cdot a$$

Question 3

A 70 kg astronaut weighs less on the Moon than on Earth. Which statement best explains why?

Accepted Answer

The gravitational acceleration on the Moon is less than on Earth.

Question 4

A 10 kg object is pulled horizontally with a force of 50 N. If the coefficient of kinetic friction between the object and the surface is 0.2, what is the acceleration of the object? (Assume $$g = 9.8\ 	ext{m/s}^2)$$

Accepted Answer

$$a = 2.0\ 	ext{m/s}^2$$

Question 5

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

Accepted Answer

For every action, there is an equal and opposite reaction acting on a different object.

Question 6

A rocket launches vertically. Which statement correctly explains its motion using Newton’s third law?

Accepted Answer

The rocket is propelled upward by the reaction force to the gases expelled downward.

Question 7

A 2 kg block sits on a 30° incline. The coefficient of static friction is 0.5. What is the minimum force required to start moving the block up the incline? (Assume $$g = 9.8\ 	ext{m/s}^2)$$

Accepted Answer

$$F = 13.7\ 	ext{N}$$

Question 8

Which of the following is NOT an inertial reference frame?

Accepted Answer

A rotating merry-go-round.

Question 9

A 3 kg object is suspended from a rope. What is the tension in the rope if the object is at rest? (Assume $$g = 9.8\ 	ext{m/s}^2)$$

Accepted Answer

$$T = 29.4\ 	ext{N}$$

Question 10

A 4 kg object is pushed across a rough surface with a constant velocity. The coefficient of kinetic friction is 0.3. What is the magnitude of the frictional force?

Accepted Answer

$$F_{	ext{friction}} = 11.76\ 	ext{N}$$

Question 11

Which equation correctly expresses the weight $$W of an $$object of mass $$m$$ near the surface of the Earth?

Accepted Answer

$$W = m \cdot g$$

Question 12

A 6 kg object is acted upon by two forces: 20 N to the right and 8 N to the left. What is the acceleration of the object?

Accepted Answer

$$a = 2\ 	ext{m/s}^2$$\ 	ext{to the right}

Question 13

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

Accepted Answer

Weight is a force, mass is a property of matter.

Question 14

A 10 kg box is pulled with a force of 40 N along a horizontal surface. If the box accelerates at $$2\ 	ext{m/s}^2$$, what is the net force acting on the box?

Accepted Answer

$$F_{	ext{net}} = 20\ 	ext{N}$$

Question 15

A person pushes a 5 kg box on a floor with a force of 25 N. The box does not move. What is the magnitude of the static friction force?

Accepted Answer

$$F_{	ext{friction}} = 25\ 	ext{N}$$

Question 16

Which of the following best describes the normal force?

Accepted Answer

A force perpendicular to the surface that balances gravity.

Question 17

A 2 kg object slides down a frictionless incline at 30°. What is the acceleration of the object along the incline?

Accepted Answer

$$a = 4.9\ 	ext{m/s}^2$$

Question 18

Which of the following is the correct expression for the kinetic friction force $$F_k$$?

Accepted Answer

$$F_k = \mu_k \cdot N$$

Question 19

A free-body diagram is used to:

Accepted Answer

Show all the forces acting on an object, including their magnitudes and directions.

Dynamics: Newton’s Laws of Motion – Structured Study Notes

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