Question 1

A car moves in a circle of radius $$r at $$constant speed $$v. $$What is the direction of the centripetal acceleration?

Accepted Answer

Radially inward toward the center

Question 2

Two small objects, with masses $$m$$ and $$M$$, are originally a distance $$r$$ apart, and the gravitational force on each has magnitude $$F. If $$the second object has its mass changed to $$2M$$, and the distance is changed to $$r/4$$, what is the magnitude of the new gravitational force?

Accepted Answer

$$32F$$

Question 3

A uniform solid cylinder of mass $$10\,\mathrm{kg}$$ can rotate about a frictionless axle through its center. A rope wrapped around the outer radius $$R_1 = 1.0$$\,\mathrm{m}$$ exerts a force of magnitude F_1$ = 5.0\,\mathrm{N} to $$the right. A second rope wrapped around another section of radius $$R_2 = 0.50$$\,\mathrm{m}$$ exerts a force of magnitude F_2$ = 6.0\,\mathrm{N}$$ downward. What is the angular acceleration of the cylinder? ($$I_{\mathrm{cylinder}} = \frac{1}{2}MR^2$)

Accepted Answer

$$1.0\,\mathrm{$$rad/s^2$$}$$

Question 4

A 1.5-kg child is sitting on a playground teeter-totter, 1.5 m from the pivot. What is the magnitude of the minimum force, applied 0.30 m on the other side of the pivot, that is needed to make the child lift off the ground?

Accepted Answer

$$75\,\mathrm{N}$$

Question 5

A pulley has an initial angular speed of $$12.5\,\mathrm{rad/s}$$ and a constant angular acceleration of $$3.41\,\mathrm{$$rad/s^2$$}. $$Through what angle does the pulley turn in $$5.26\,\mathrm{s}$$?

Accepted Answer

$$122\,\mathrm{rad}$$

Question 6

A 3.0-m-long ladder, weighing $$200\,\mathrm{N}$$, leans against a smooth vertical wall with its base on a horizontal rough floor, a distance of $$1.00\,\mathrm{m}$$ away from the wall. The ladder is not completely uniform, so its center of gravity is $$1.0\,\mathrm{m}$$ from its base. What force of friction must the floor exert at the base of the ladder to prevent the ladder from sliding down?

Accepted Answer

$$93.3\,\mathrm{N}$$

Question 7

A 1.0-kg mass is located at $$(0.0\,\mathrm{m}, 8.0\,\mathrm{m})$$, and a 1.0-kg mass is located at $$(12.0\,\mathrm{m}, 0.0\,\mathrm{m}). $$You want to add a 4.0-kg mass so that the center of mass (or center of gravity) of the three-mass system will be at the origin. What should be the coordinates of the 4.0-kg mass?

Accepted Answer

$$(0.0\,\mathrm{m}, 0.0\,\mathrm{m})$$

Question 8

A drive chain in a bicycle is applying a torque of $$0.850\,\mathrm{N \cdot m} to $$the wheel of the bicycle. You can treat the wheel as a thin uniform hoop (or ring) with a mass of $$0.750\,\mathrm{kg}$$ and a radius of $$33.0\,\mathrm{cm}. $$What is the angular acceleration of the wheel?

Accepted Answer

$$4.13\,\mathrm{$$rad/s^2$$}$$

Question 9

A 20-m piano wire has a radius of $$0.50\,\mathrm{mm}. $$One end is fixed and the other is wrapped around a tuning peg, which has a diameter of $$3.5\,\mathrm{mm}$$ and is $$80\,\mathrm{cm}$$ away. After the wire just becomes taut, the peg is given three full turns. What is the tension in the wire? Young's modulus for steel is $$2.0 	imes 10$$^{11}$$\,\mathrm{N/m^2$}.$$

Accepted Answer

$$6.5\,\mathrm{kN}$$

Question 10

A store's sign has a mass of $$20\,\mathrm{kg}$$ and is $$3.0\,\mathrm{m}$$ long. It is uniform, so its center of gravity is at the center of the sign. It is supported horizontally by a small loose bolt attached to the wall at one end, and by a wire at the other end, as shown in the figure. What is the tension in the wire?

Accepted Answer

$$320\,\mathrm{N}$$

Question 11

A man in a gym is holding an $$8.0\,\mathrm{kg}$$ weight at arm's length, a distance of $$0.55\,\mathrm{m}$$ from his shoulder joint. What is the torque about his shoulder joint due to the weight if his arm is held at $$30^\circ$$ below the horizontal?

Accepted Answer

$$37\,\mathrm{N \cdot m}$$

Question 12

A 1.0-m-high refrigerator has a mass of $$20\,\mathrm{kg}$$ and is $$1.0\,\mathrm{m}$$ long. Its center of gravity is at the center of the sign. If it is supported horizontally by a small loose bolt attached to the wall at one end, and by a wire at the other end, as shown in the figure. What is the tension in the wire?

Accepted Answer

$$1.6\,\mathrm{m}$$

Question 13

A light ideal spring stretches by $$21.0\,\mathrm{cm}$$ when it is used to hang a $$135\,\mathrm{N}$$ object. What is the weight of a piece of electronic equipment that would stretch the spring by $$4.4\,\mathrm{cm} if $$you hang the equipment using the spring?

Accepted Answer

$$28\,\mathrm{N}$$

Question 14

A compact disc is rotating at $$210\,\mathrm{rpm}. $$What is its angular speed in rad/s?

Accepted Answer

$$22\,\mathrm{rad/s}$$

Question 15

When a fan is turned off, its angular speed decreases from $$10.0\,\mathrm{rad/s} to$$ $$6.3\,\mathrm{rad/s} in$$ $$5.0\,\mathrm{s}. $$What is the magnitude of the average angular acceleration of the fan?

Accepted Answer

$$0.74\,\mathrm{$$rad/s^2$$}$$

Question 16

An irregularly shaped object that is $$10\,\mathrm{m}$$ long is placed with each end on a scale. If the scale on the right reads $$4\,\mathrm{N}$$ while the scale on the left reads $$7\,\mathrm{N}$$, how far from the left end is the center of gravity of this object?

Accepted Answer

$$4.7\,\mathrm{m}$$

Question 17

A 4.0-kg mass is located at $$(0.0\,\mathrm{m}, 0.0\,\mathrm{m})$$, a 1.0-kg mass is located at $$(0.0\,\mathrm{m}, 8.0\,\mathrm{m})$$, and a 1.0-kg mass is located at $$(12.0\,\mathrm{m}, 0.0\,\mathrm{m}). $$What are the coordinates of the center of mass of the system?

Accepted Answer

$$(2.0\,\mathrm{m}, 1.6\,\mathrm{m})$$

Fundamental Concepts and Problem Solving in College Physics

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드