Question 1

A 50.0-g salt shaker is slid across a table with an initial speed of 1.15 m/s and comes to rest due to friction. If the coefficient of kinetic friction between the shaker and the table is $$\mu_k = 0.25$$, what is the magnitude of the frictional force acting on the shaker?

Accepted Answer

$$f_k = 0.12\ \mathrm{N}$$

Question 2

Which of the following best describes the role of static friction when a force is applied to an object at rest?

Accepted Answer

It adjusts up to a maximum value to prevent motion, depending on the applied force.

Question 3

A gardener uses two wires to support a pot of flowers. One wire is horizontal, and the other makes an angle of $$40.0^\circ$$ with the ceiling. If the pot has a mass of $$2.0\ \mathrm{kg}$$, what is the tension in the angled wire?

Accepted Answer

$$T = \dfrac{mg}{\sin 40.0^\circ}$$

Question 4

Which equation correctly expresses the force exerted by an ideal spring according to Hooke's Law?

Accepted Answer

$$F = kx$$

Question 5

A crate begins to slide down a tilted bed when the angle reaches $$23.5^\circ. $$What is the coefficient of static friction between the crate and the bed?

Accepted Answer

$$\mu_s = 	an 23.5^\circ$$

Question 6

A 95.0-kg crate is at rest on a ramp. If the coefficient of static friction is $$\mu_s = 0.30$$, what is the maximum angle $$	heta at $$which the crate will remain at rest?

Accepted Answer

$$	heta = \arctan(0.30)$$

Question 7

A centrifuge rotates such that the bottom of a test tube moves at $$v = 90.6\ \mathrm{m/s}$$ and is $$r = 9.25\ \mathrm{cm}$$ from the axis. What is the centripetal acceleration at the bottom of the tube?

Accepted Answer

$$a_c = \dfrac{v^2$}{r}$$

Question 8

Which statement about the tension in a real rope is correct?

Accepted Answer

Tension varies along the rope due to its weight.

Question 9

Two boxes of masses $$m_1$$ and $$m_2$$ are connected by a string and pulled by a force $$F. If $$the system accelerates at $$a$$, what is the tension $$T in $$the string between the boxes?

Accepted Answer

$$T = m_1$ a$$

Question 10

An object slides down a $$3.0\ \mathrm{m}$$ ramp inclined at $$23^\circ$$ with a coefficient of kinetic friction $$\mu_k = 0.15. $$How much time does it take to reach the bottom if it starts from rest?

Accepted Answer

$$t = \sqrt{\dfrac{2d}{g(\sin 23^\circ - \mu_k \cos 23^\circ)}}$$

Question 11

Which of the following is true about translational equilibrium?

Accepted Answer

The net force acting on the object is zero.

Question 12

A block is pulled across a rough surface at constant speed. Which statement is correct about the forces acting on the block?

Accepted Answer

The applied force equals the kinetic frictional force.

Question 13

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

Accepted Answer

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

Question 14

Which of the following is NOT a property of the static frictional force?

Accepted Answer

It always equals $$\mu_s N$$ regardless of the situation.

Question 15

A device with three pulleys is used to apply a force to a broken leg. If the tension in the rope is $$165\ \mathrm{N}$$, what mass $$m$$ must be hung from the rope to achieve this tension? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$m = \dfrac{165}{9.8}\ \mathrm{kg}$$

Question 16

Which formula gives the magnitude of the centripetal force required to keep an object of mass $$m$$ moving in a circle of radius $$r at $$speed $$v$$?

Accepted Answer

$$F_c = m \dfrac{v^2$}{r}$$

Question 17

A block of mass $$m is $$connected to another block of mass $$M by a $$string over a frictionless pulley. If $$M \u003e m$$, what is the acceleration of the system?

Accepted Answer

$$a = \dfrac{(M - m)g}{M + m}$$

Question 18

Which of the following statements about kinetic friction is correct?

Accepted Answer

It depends on the normal force and the coefficient of kinetic friction.

Applications of Newton’s Laws – Chapter 6 Study Notes

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