1. Physics of Everyday Phenomena
W. Thomas Griffith
Juliet W. Brosing
Chapter 8
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Question 8.1
Which of the following is NOT a unit for rotational displacement?
Degrees
Rad/s
Revolutions
radians

3. Question 8.2 Which of the following is a unit for rotational velocity?
hours/radians
Radians
Rev/sec
degrees

4. Question 8.3
A CD makes one complete revolution every tenth of a second. The angular velocity of point 4 is:
A) the same as for pt 1.
B) twice that of pt 2.
C) half that of pt 2.
D) 1/4 that of pt 1.
E) four times that of pt 1.

5. Question 8.4
A CD makes one complete revolution every tenth of a second. Which has the largest linear (tangential) velocity?
A) point 1
B) point 2
C) point 3
D) point 4

6. Question 8.5
Which object has the largest magnitude of rotational acceleration?
An object starting from rest and reaching 2 rev/s in 20 sec
An object rotating at 3 rev/s and coming to a stop in 10 sec
An object rotating at a constant 4 rev/s

7. Question 8.6
When using the equation that relates linear speed and rotational velocity (v = r) what are acceptable units for the rotational velocity () ?
degrees/s
Radians/min
Rev/min (rpm)

8. Question 8.7
If two children sit on a seesaw and one is twice as heavy as the other, in order to achieve
balance the lighter child must sit
A) half as far from the fulcrum
B) twice as far from the fulcrum
C) the same distance from the fulcrum
D) four times as far from the fulcrum

9. Question 8.8 To increase the applied torque one can Increase the force
Increase the lever arm by moving to the end of the lever
Increase the lever arm by applying the force perpendicularly to the lever
All of the above
None of the above

10. Question 8.9
The point in or near an object about which the weight of the object itself exerts no net
torque is the
A) impulse point
B) fulcrum
C) center of gravity

11. Question 8.10
If the distance between a point mass and the pivot point is tripled, the rotational inertia
of the object about that point is multiplied by
A) 9
B) 3
C) 1/3
D) 1/9

12. Question 8.11
Which rod has the smallest rotational inertia, I, the one rotating about the end, or the one rotating about the center?
Rotating about end
Rotating through center
They both have the same I, since they have the same mass and length

13. Question 8.12
Two objects, a ring and a disk, both with equal mass and radii. Each is rotating about an axis through its center, as shown. Which has the greatest rotational inertia, I, a uniform disk or a ring?
They have the same I, since they both have the same mass and radius
The disk
The ring

14. Question 8.13
Which will win the race to the bottom of the incline: a hoop, or a disk with the same mass and radius?
A) the hoop
B) the disk
C) they will both reach the bottom at the same time

15. Question 8.14 Angular momentum is calculated as the
A) product of mass times velocity
B) product of mass times angular velocity
C) product of moment of inertia times velocity
D) product of moment of inertia times angular velocity

16. Question 8.15 Angular momentum is conserved
A) only when the net force acting on the system is zero
B) only when the angular velocity is zero
C) only when the net torque acting on the system is zero
D) in all cases

17. Question 8.16
A figure skater spins with her arms extended. When she pulls in her arms, she spins faster
because
A) she has decreased her rotational inertia.
B) she has increased her rotational inertia.
C) she has increased her angular momentum.
D) the ice exerts a torque on her skates.

18. Question 8.17
Meredith sits in the middle of a merry-go-round that her brother Kiel is pushing. If
Meredith moves to the outer edge of the merry-go-round, it will
A) speed up.
B) slow down.
C) spin at the same rate.

19. Question 8.18
What is the direction of the angular momentum vector for a wheel spinning as shown below?
Upward
Downward
Clockwise
Counterclockwise

20. Question 8.19
As we learned in Chapter 5, the gravitational force between the earth and the sun supplies the centripetal force which causes the Earth to rotate about the sun. Does this force produce a torque about the sun? No
Yes

21. Question 8.20
As a planet moves closer to the sun in its elliptical orbit its rotational velocity increases. Is angular momentum conserved?
Yes No

22. Question 8.21 When angular momentum is conserved
The magnitude of the total angular momentum remains constant
The direction of the total angular momentum remains constant
The magnitude and direction of the total angular momentum remains constant

23. Answer Key to Chapter 8 B C A D C B D A