Q: Which equation correctly represents the balance of forces for block A sliding at constant speed down the incline?

$$m g \sin \theta = \mu_k m g \cos \theta$$

Question 1

A block A (weight 1.00 kg) rests on a horizontal surface and is connected by a light, flexible cord passing over a frictionless pulley to block B (weight 2.00 N), which hangs vertically. If the coefficient of kinetic friction between block A and the surface is $$\mu_k = 0.30$$, what is the acceleration of the system when released from rest?

Accepted Answer

$$a = 0.51\ \mathrm{m/s^2$}$$

Question 2

Given the same system as above, what is the tension $$T in $$the cord connecting blocks A and B?

Accepted Answer

$$T = 1.49\ \mathrm{N}$$

Question 3

If the coefficient of kinetic friction between block A and the surface is increased to $$\mu_k = 0.50$$, what happens to the acceleration of the system?

Accepted Answer

The acceleration decreases.

Question 4

Block A (weight $$2\ \mathrm{N}) $$slides down an inclined plane of slope angle $$36.9^\circ at $$constant speed. What is the coefficient of kinetic friction $$\mu_k$$ between block A and the plane?

Accepted Answer

$$\mu_k = 	an 36.9^\circ$$

Question 5

If block A is moving at constant speed down the incline, what is the net force acting on it along the direction of motion?

Accepted Answer

$$F_{	ext{net}} = 0$$

Question 6

For the inclined plane scenario, which of the following best describes the direction of the frictional force acting on block A?

Accepted Answer

Up the incline, opposing the motion.

Question 7

If the angle of the incline is increased while keeping $$\mu_k$$ constant, what happens to the acceleration of block A?

Accepted Answer

The acceleration increases.

Question 8

Which equation correctly represents the balance of forces for block A sliding at constant speed down the incline?

Accepted Answer

$$m g \sin 	heta = \mu_k m g \cos 	heta$$

Question 9

In the horizontal pulley system, if block B is replaced with a heavier block, what happens to the acceleration of the system?

Accepted Answer

The acceleration increases.

Question 10

A student claims that the tension in the cord is equal to the weight of block B in the horizontal pulley system. Is this correct?

Accepted Answer

No, because friction and the mass of block A must be considered.

Question 11

If the cord in the horizontal pulley system is not massless, how does this affect the tension throughout the cord?

Accepted Answer

The tension varies along the length of the cord.

Question 12

Which of the following best describes the normal force acting on block A on the incline?

Accepted Answer

$$N = m g \cos 	heta$$

Question 13

If the coefficient of kinetic friction is zero, what is the acceleration of block A down the incline?

Accepted Answer

$$a = g \sin 	heta$$

Question 14

In the horizontal pulley system, if the coefficient of kinetic friction is zero, what is the acceleration of the system?

Accepted Answer

$$a = \frac{W_B}{m_A}$$

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