Q: A 5 kg object is hanging at rest from a rope. What is the tension in the rope? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

$$T = 5 \times 9.8 = 49\ \mathrm{N}$$

Q: A runner pushes against the starting block with a force at an angle $$\theta$$ above the horizontal. Which component of this force is responsible for the runner's forward acceleration?

The horizontal component, $$F \cos \theta$$

Question 1

Which of the following statements best describes a force in physics?

Accepted Answer

A force is a vector quantity that represents a push or pull, with both magnitude and direction.

Question 2

A 10 N force is applied to a box at an angle of $$30^\circ$$ above the horizontal. What is the horizontal component of this force?

Accepted Answer

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

Question 3

Which of the following is NOT a contact force?

Accepted Answer

Weight (gravitational force)

Question 4

A hockey puck on a frictionless surface is acted on by two equal and opposite horizontal forces. What is the resulting acceleration of the puck?

Accepted Answer

The puck remains at rest or moves with constant velocity.

Question 5

A 2 kg object is acted on by a net force of 6 N. What is its acceleration?

Accepted Answer

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

Question 6

A block of mass $$m is $$pulled by a rope with tension $$T at an $$angle $$	heta$$ above the horizontal. Which equation gives the vertical component of the tension?

Accepted Answer

$$T \sin 	heta$$

Question 7

A 5 kg object is hanging at rest from a rope. What is the tension in the rope? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$T = 5 	imes 9.8 = 49\ \mathrm{N}$$

Question 8

A runner pushes against the starting block with a force at an angle $$	heta$$ above the horizontal. Which component of this force is responsible for the runner's forward acceleration?

Accepted Answer

The horizontal component, $$F \cos 	heta$$

Question 9

A block of mass $$m_1 = 1$$\ \mathrm{kg}$$ is accelerated at a_1$ = 5\ \mathrm{m/s^2$} by a $$force $$F. $$The same force is applied to a second block, producing an acceleration $$a_2 = 1$$\ \mathrm{$$m/s^2$$}$$. What is the mass m_2$ of the second block?

Accepted Answer

$$m_2 = 5$$\ \mathrm{kg}$$

Question 10

A basketball player jumps by pushing down on the floor. According to Newton's third law, what is the reaction force?

Accepted Answer

The upward normal force exerted by the floor on the player

Question 11

A 3 kg object moves in a circle of radius 2 m at constant speed. If the net force required for this motion is 18 N, what is the magnitude of the acceleration?

Accepted Answer

$$a = \frac{18}{3} = 6\ \mathrm{m/s^2$}$$

Question 12

A child and sled (total mass 40 kg) slide at constant velocity across snow. The forward force from an adult's foot is 60 N. What is the force of friction acting on the sled?

Accepted Answer

60 N

Question 13

Which of the following best describes the normal force acting on a box resting on an inclined plane?

Accepted Answer

It acts perpendicular to the surface and supports the box against gravity.

Question 14

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

Accepted Answer

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

Question 15

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

Accepted Answer

The acceleration due to gravity $$g is $$less on the Moon.

Question 16

If a net force of 20 N acts on a 4 kg object, what is the resulting acceleration?

Accepted Answer

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

Question 17

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

Accepted Answer

The normal force equals the weight of the block.

Question 18

A car of mass 1000 kg accelerates from rest under a net force of 4000 N. What is its acceleration?

Accepted Answer

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

Newton's Laws of Motion and the Concept of Force

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