Q: A block is sliding down a rough incline with angle $$\theta$$ and coefficient of kinetic friction $$\mu_k. $$What is the expression for the acceleration of the block?

$$a = g (\sin \theta - \mu_k \cos \theta)$$

Q: Which of the following is the correct expression for the net force acting on an object sliding down an inclined plane with friction?

$$F_{net} = m g \sin \theta - \mu_k m g \cos \theta$$

Question 1

A box of mass $$m is $$resting on a horizontal surface. If the coefficient of static friction between the box and the surface is $$\mu_s$$, what is the maximum force that can be applied horizontally before the box starts to move?

Accepted Answer

$$F_{max} = \mu_s m g$$

Question 2

A 10 kg box is pulled up a frictionless incline at an angle $$	heta = 30^\circ$$ with respect to the horizontal. What is the magnitude of the force parallel to the incline required to move the box at constant velocity?

Accepted Answer

$$F = m g \sin 	heta$$

Question 3

Which of the following best describes the normal force acting on an object of mass $$m$$ resting on a horizontal surface?

Accepted Answer

$$F_N = m g$$

Question 4

A block is sliding down a rough incline with angle $$	heta$$ and coefficient of kinetic friction $$\mu_k. $$What is the expression for the acceleration of the block?

Accepted Answer

$$a = g (\sin 	heta - \mu_k \cos 	heta)$$

Question 5

If a force $$F is $$applied at an angle $$	heta$$ above the horizontal to a box on a flat surface, what is the vertical component of the force?

Accepted Answer

$$F_y = F \sin 	heta$$

Question 6

A 5 kg object is suspended by two ropes, each making an angle of $$45^\circ$$ with the ceiling. What is the tension in each rope?

Accepted Answer

$$T = \frac{m g}{2 \sin 45^\circ}$$

Question 7

Which of the following statements about friction is correct?

Accepted Answer

Kinetic friction acts when an object is moving, and static friction acts when it is at rest.

Question 8

A car of mass $$m is $$parked on a hill inclined at angle $$	heta. $$What is the minimum coefficient of static friction $$\mu_s$$ required to prevent the car from sliding down?

Accepted Answer

$$\mu_s = 	an 	heta$$

Question 9

A block is connected to a spring and oscillates horizontally on a frictionless surface. Which force is responsible for the block's acceleration?

Accepted Answer

The restoring force of the spring, $$F = -k x$$

Question 10

A 2 kg block is pulled by a force of 10 N at an angle of $$60^\circ$$ above the horizontal. What is the horizontal component of the force?

Accepted Answer

$$F_x = 10 \cos 60^\circ$$

Question 11

Which of the following is the correct expression for the net force acting on an object sliding down an inclined plane with friction?

Accepted Answer

$$F_{net} = m g \sin 	heta - \mu_k m g \cos 	heta$$

Question 12

A rope pulls a crate of mass $$m$$ across a rough floor at constant velocity. If the coefficient of kinetic friction is $$\mu_k$$, what is the tension in the rope?

Accepted Answer

$$T = \mu_k m g$$

Question 13

A block of mass $$m is $$hanging from a rope. If the block is at rest, what is the tension in the rope?

Accepted Answer

$$T = m g$$

Question 14

Which of the following best describes the direction of the normal force on an inclined plane?

Accepted Answer

Perpendicular to the surface of the incline

Question 15

A 3 kg block is at rest on a horizontal surface. If a horizontal force of 20 N is applied and the coefficient of static friction is 0.5, will the block move?

Accepted Answer

No, because $$F_{applied} \u003c F_{max,static}$$

Question 16

A block is pulled at constant speed up a rough incline. Which of the following is true about the forces acting on the block?

Accepted Answer

The sum of the pulling force and friction equals the component of gravity down the incline.

Study Notes: Newton's Laws of Motion and Types of Forces

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