Q: A 1000 kg car moves around a circular track of radius 50 m at a constant speed of 20 m/s. What is the magnitude of the net force acting on the car?

$$F = m \cdot a_{rad} = 1000 \times \frac{20^2$}{50} = 4000\ \text{N}$$

Q: A block is pulled by a rope with a force of 10 N at an angle of $$30^\circ$$ above the horizontal. What is the vertical component of the force?

$$10 \sin 30^\circ = 5.0\ \text{N}$$

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

$$a = \frac{F}{m} = \frac{8}{2} = 4\ \text{m/s}^2$$

Q: A 5 kg object is moving in a circle of radius 2 m at a constant speed of 4 m/s. What is the magnitude of its centripetal acceleration?

$$a_{rad} = \frac{v^2$}{R} = \frac{16}{2} = 8\ \text{m/s}^2$$

Q: A block is pulled with a force of 10 N at $$30^\circ$$ above the horizontal. What is the horizontal component of the force?

$$10 \cos 30^\circ = 8.66\ \text{N}$$

Question 1

A car is moving in a circle at constant speed. Which of the following statements about its acceleration is correct?

Accepted Answer

The acceleration is directed toward the center of the circle and is perpendicular to the velocity.

Question 2

A 1000 kg car moves around a circular track of radius 50 m at a constant speed of 20 m/s. What is the magnitude of the net force acting on the car?

Accepted Answer

$$F = m \cdot a_{rad} = 1000 	imes \frac{20^2$}{50} = 4000\ 	ext{N}$$

Question 3

Which of the following best describes the direction of the velocity and acceleration vectors for an object in uniform circular motion?

Accepted Answer

Velocity is tangent to the circle, acceleration is toward the center.

Question 4

A battleship fires two shells at ships A and B. Both shells are fired simultaneously and land at the same time. What can you conclude about the vertical motion of the shells?

Accepted Answer

Both shells have the same vertical displacement and experience the same acceleration due to gravity.

Question 5

A block is pulled by a rope with a force of 10 N at an angle of $$30^\circ$$ above the horizontal. What is the vertical component of the force?

Accepted Answer

$$10 \sin 30^\circ = 5.0\ 	ext{N}$$

Question 6

Which of the following is NOT a contact force?

Accepted Answer

Weight (gravitational force)

Question 7

A block rests on a horizontal surface. Which force is responsible for supporting the block against gravity?

Accepted Answer

Normal force

Question 8

According to Newton’s first law, what happens to an object if the net force acting on it is zero?

Accepted Answer

It will move with constant velocity or remain at rest.

Question 9

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

Accepted Answer

$$a = \frac{F}{m} = \frac{8}{2} = 4\ 	ext{m/s}^2$$

Question 10

A block is pulled by two forces: $$F_1 = 10$$\ 	ext{N}$$ to the right and F_2$ = 6\ 	ext{N} to $$the left. What is the net force acting on the block?

Accepted Answer

$$4\ 	ext{N} to $$the right

Question 11

Which of the following statements about Newton’s third law is correct?

Accepted Answer

Action and reaction forces are always equal in magnitude and opposite in direction.

Question 12

A 5 kg object is moving in a circle of radius 2 m at a constant speed of 4 m/s. What is the magnitude of its centripetal acceleration?

Accepted Answer

$$a_{rad} = \frac{v^2$}{R} = \frac{16}{2} = 8\ 	ext{m/s}^2$$

Question 13

A block is pulled with a force of 10 N at $$30^\circ$$ above the horizontal. What is the horizontal component of the force?

Accepted Answer

$$10 \cos 30^\circ = 8.66\ 	ext{N}$$

Question 14

A 3 kg object is at rest on a frictionless surface. Two forces act on it: $$F_1 = 6$$\ 	ext{N}$$ east and F_2$ = 8\ 	ext{N}$$ north. What is the magnitude of the net acceleration?

Accepted Answer

$$a = \frac{\sqrt{6^2$ + 8^2$}}{3} = \frac{10}{3} = 3.33\ 	ext{m/s}^2$$

Question 15

A block is at rest on a horizontal surface. Which of the following statements is true?

Accepted Answer

The normal force is equal to the weight.

Question 16

A child slides down a snowy hill on a sled. Which force is responsible for the sled’s acceleration down the hill?

Accepted Answer

Component of gravity parallel to the hill

Question 17

A block is pulled by a rope with a force of 10 N at an angle of $$30^\circ$$ above the horizontal. What is the sum of the horizontal and vertical components of the force?

Accepted Answer

$$10 \cos 30^\circ + 10 \sin 30^\circ = 8.66 + 5.0 = 13.66\ 	ext{N}$$

Question 18

A 2 kg puck on a frictionless surface is acted on by a single horizontal force of 6 N. What is the acceleration of the puck?

Accepted Answer

$$a = \frac{6}{2} = 3\ 	ext{m/s}^2$$

Motion in a Plane and Newton's Laws: Study Notes for College Physics I

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