Question 1

A block of mass $$m is $$resting on a horizontal table. If the block is pulled by a force $$F at an $$angle $$	heta$$ above the horizontal, which equation correctly represents the normal force $$n$$ acting on the block?

Accepted Answer

$$n = mg - F \sin 	heta$$

Question 2

A 2 kg block is attached to a spring with a spring constant $$k = 100 \ \mathrm{N/m}. If $$the spring is stretched by $$0.1 \ \mathrm{m}$$, what is the magnitude of the restoring force according to Hooke's Law?

Accepted Answer

$$F = 10 \ \mathrm{N}$$

Question 3

Which of the following statements about tension in an ideal rope (massless and inextensible) is correct?

Accepted Answer

Tension is the same at every point along the rope.

Question 4

A box of mass $$m is at $$rest on an inclined plane that makes an angle $$	heta$$ with the horizontal. Which equation gives the normal force $$n$$ acting on the box?

Accepted Answer

$$n = mg \cos 	heta$$

Question 5

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

Accepted Answer

$$T = 49 \ \mathrm{N}$$

Question 6

Which of the following best describes the direction of the frictional force acting on a moving object?

Accepted Answer

It acts opposite to the direction of motion.

Question 7

A 10 kg box is pulled across a horizontal surface with a force of $$60 \ \mathrm{N} at an $$angle of $$30^\circ$$ above the horizontal. If the coefficient of kinetic friction is $$0.2$$, what is the frictional force acting on the box? (Take $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$f_k = 16.96 \ \mathrm{N}$$

Question 8

Which equation correctly expresses the gravitational force between two masses $$m_1$$ and $$m_2$$ separated by a distance $$r$$?

Accepted Answer

$$F_g = G \dfrac{m_1$ m_2$}{r^2$}$$

Question 9

A person pushes a box but it does not move. Which force is responsible for preventing the box from moving?

Accepted Answer

Static friction

Question 10

A spring with a spring constant $$k = 200 \ \mathrm{N/m} is $$compressed by $$0.05 \ \mathrm{m}. $$What is the force exerted by the spring?

Accepted Answer

$$F = -10 \ \mathrm{N}$$

Question 11

A 3 kg block is suspended by a rope and is accelerating upward at $$2 \ \mathrm{m/s^2$}. $$What is the tension in the rope? (Take $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$T = 35.4 \ \mathrm{N}$$

Question 12

Which of the following is NOT a correct statement about the normal force?

Accepted Answer

It always equals the weight of the object.

Question 13

A block is sliding down a frictionless inclined plane. Which force is responsible for the block's acceleration down the plane?

Accepted Answer

Component of gravity parallel to the plane

Question 14

If the gravitational force between two objects is $$10 \ \mathrm{N}$$ when they are $$2 \ \mathrm{m}$$ apart, what will the force be if the distance is doubled?

Accepted Answer

$$2.5 \ \mathrm{N}$$

Question 15

A box is pulled with a force $$F at an $$angle $$	heta$$ above the horizontal. Which component of the force acts to move the box horizontally?

Accepted Answer

$$F \cos 	heta$$

Question 16

Which of the following best describes static friction?

Accepted Answer

It acts to prevent the start of motion between two surfaces.

Question 17

A 4 kg block is pulled across a rough surface with a constant velocity. If the coefficient of kinetic friction is $$0.25$$, what is the magnitude of the frictional force? (Take $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$f_k = 10 \ \mathrm{N}$$

Question 18

Which of the following is the correct expression for the weight of an object of mass $$m on $$Earth?

Accepted Answer

$$W = mg$$

Question 19

A block is attached to a spring and pulled so that it stretches by $$x. If $$the spring constant is doubled, what happens to the restoring force for the same displacement?

Accepted Answer

It is doubled.

Question 20

A 6 kg box is suspended by a rope and is accelerating downward at $$2 \ \mathrm{m/s^2$}. $$What is the tension in the rope? (Take $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$T = 47.8 \ \mathrm{N}$$

Applying Newton’s Laws: Forces and Free Body Diagrams

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