Q: A 5 kg box sits on the floor. What is the weight of the box on Earth?

$$F_g = 5\ \mathrm{kg} \times 9.8\ \mathrm{m/s^2$} = 49\ \mathrm{N}$$

Q: A 10 kg box is on the moon, where $$g = 1.62\ \mathrm{m/s^2$}. $$What is the weight of the box?

$$F_g = 10\ \mathrm{kg} \times 1.62\ \mathrm{m/s^2$} = 16.2\ \mathrm{N}$$

Q: A 10 kg box is at rest on a table. What is the normal force acting on the box?

$$F_N = 10\ \mathrm{kg} \times 9.8\ \mathrm{m/s^2$} = 98\ \mathrm{N}$$

Q: A 10 kg box is at rest on a horizontal surface. The coefficient of static friction is $$\mu_s = 0.2. $$What is the maximum static friction force?

$$F_{\text{static max}} = \mu_s F_N = 0.2 \times 98 = 19.6\ \mathrm{N}$$

Q: A 2 kg mosquito flying with an acceleration of $$0.05\ \mathrm{m/s^2$}$$ strikes a 3500 kg truck at rest. What is the magnitude of the force exerted on the truck during the collision?

$$F = 2\ \mathrm{kg} \times 0.05\ \mathrm{m/s^2$} = 0.1\ \mathrm{N}$$

Question 1

A 10 kg box is at rest on a smooth horizontal surface. Two forces are applied: 50 N to the right and 10 N to the left. What is the acceleration of the box?

Accepted Answer

$$a = \dfrac{50 - 10}{10} = 4\ \mathrm{m/s^2$}$$

Question 2

A 5 kg box sits on the floor. What is the weight of the box on Earth?

Accepted Answer

$$F_g = 5\ \mathrm{kg} 	imes 9.8\ \mathrm{m/s^2$} = 49\ \mathrm{N}$$

Question 3

A 10 kg box is on the moon, where $$g = 1.62\ \mathrm{m/s^2$}. $$What is the weight of the box?

Accepted Answer

$$F_g = 10\ \mathrm{kg} 	imes 1.62\ \mathrm{m/s^2$} = 16.2\ \mathrm{N}$$

Question 4

A 2 kg object is acted on by a force of 7 N to the right and 3 N to the left. What is the acceleration of the object?

Accepted Answer

$$a = \dfrac{7 - 3}{2} = 2\ \mathrm{m/s^2$}$$

Question 5

A 10 kg box is at rest on a table. What is the normal force acting on the box?

Accepted Answer

$$F_N = 10\ \mathrm{kg} 	imes 9.8\ \mathrm{m/s^2$} = 98\ \mathrm{N}$$

Question 6

A 10 kg box is at rest on a horizontal surface. The coefficient of static friction is $$\mu_s = 0.2. $$What is the maximum static friction force?

Accepted Answer

$$F_{	ext{static max}} = \mu_s F_N = 0.2 	imes 98 = 19.6\ \mathrm{N}$$

Question 7

A 20 kg object is pulled across a floor with a force of 50 N at an angle of $$50^\circ$$ above the horizontal. What is the horizontal component of the force?

Accepted Answer

$$F_x = 50 \cos 50^\circ = 32.14\ \mathrm{N}$$

Question 8

A 500 g object is acted on by a 5 N force to the left and a 9 N force to the right. What is the acceleration of the object?

Accepted Answer

$$a = \dfrac{9 - 5}{0.5} = 8\ \mathrm{m/s^2$}$$

Question 9

A tennis player’s racket applies an average force of 200 N to a tennis ball for 0.025 s. Compared to the average force exerted by the racket on the tennis ball, the force of the tennis ball on the racket is:

Accepted Answer

The same

Question 10

A 2 kg mosquito flying with an acceleration of $$0.05\ \mathrm{m/s^2$}$$ strikes a 3500 kg truck at rest. What is the magnitude of the force exerted on the truck during the collision?

Accepted Answer

$$F = 2\ \mathrm{kg} 	imes 0.05\ \mathrm{m/s^2$} = 0.1\ \mathrm{N}$$

Question 11

A 5 kg bullet experiences a force of 650 N. What will be the acceleration of the bullet?

Accepted Answer

$$a = \dfrac{650}{5} = 130\ \mathrm{m/s^2$}$$

Question 12

A 65 kg person fires a 5 kg bullet with a force of 650 N. What is the recoil acceleration experienced by the person?

Accepted Answer

$$a = \dfrac{650}{65} = 10\ \mathrm{m/s^2$}$$

Question 13

A 50 kg box is pulled across a rough surface with a force of 75 N at an angle of $$40^\circ at $$constant velocity. What is the magnitude of the force of friction acting on the object?

Accepted Answer

$$F_{	ext{friction}} = 75 \cos 40^\circ = 57.45\ \mathrm{N}$$

Question 14

A 7.5 kg box experiences two forces: 10 N to the right and 34.64 N to the left. What is the magnitude of the acceleration of the box?

Accepted Answer

$$a = \dfrac{34.64 - 10}{7.5} = 3.26\ \mathrm{m/s^2$}$$

Question 15

Which of the following statements accurately describes Newton's 3rd Law?

Accepted Answer

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

Question 16

A 1500 kg car is required to accelerate at $$2\ \mathrm{m/s^2$}. $$How much force is required?

Accepted Answer

$$F = 1500 	imes 2 = 3000\ \mathrm{N}$$

Question 17

Four objects of equal mass are acted on by forces of 10 N, 20 N, 25 N, and 5 N. What is the order of their acceleration from smallest to greatest?

Accepted Answer

5 N, 10 N, 20 N, 25 N

Question 18

A 6 kg object is being pulled with a force of 24 N at an angle of $$30^\circ$$ across a surface. What is the acceleration of the object?

Accepted Answer

$$a = \dfrac{24 \cos 30^\circ}{6} = 3.46\ \mathrm{m/s^2$}$$

Forces and Newton's Laws: Study Guide with Applications and Problem Solving

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