1. © 2015 Pearson Education, Inc.

2. QuickCheck 7.1
A ball rolls around a circular track with an angular velocity of 4 rad/s. What is the period of the motion? s
1 s
2 s
Answer: A
© 2015 Pearson Education, Inc.

3. QuickCheck 7.1
A ball rolls around a circular track with an angular velocity of 4 rad/s. What is the period of the motion? s
1 s
2 s
© 2015 Pearson Education, Inc.

4. QuickCheck 7.2
Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s angular velocity is ______ that of Rasheed.
Half
The same as
Twice
Four times
We can’t say without knowing their radii.
Answer: B
© 2015 Pearson Education, Inc.

5. QuickCheck 7.2
Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s angular velocity is ______ that of Rasheed.
Half
The same as
Twice
Four times
We can’t say without knowing their radii.
© 2015 Pearson Education, Inc.

6. QuickCheck 7.3
Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s speed is ______ that of Rasheed.
Half
The same as
Twice
Four times
We can’t say without knowing their radii.
Answer: C
© 2015 Pearson Education, Inc.

7. QuickCheck 7.3
Rasheed and Sofia are riding a merry-go-round that is spinning steadily. Sofia is twice as far from the axis as is Rasheed. Sofia’s speed is ______ that of Rasheed.
Half
The same as
Twice v = ωr
Four times
We can’t say without knowing their radii.
© 2015 Pearson Education, Inc.

8. QuickCheck 7.4
Two coins rotate on a turntable. Coin B is twice as far from the axis as coin A.
The angular velocity of A is twice that of B
The angular velocity of A equals that of B
The angular velocity of A is half that of B
Answer: B
© 2015 Pearson Education, Inc. 8

9. QuickCheck 7.4
Two coins rotate on a turntable. Coin B is twice as far from the axis as coin A.
The angular velocity of A is twice that of B
The angular velocity of A equals that of B
The angular velocity of A is half that of B
© 2015 Pearson Education, Inc. 9

10. QuickCheck 7.5
The fan blade is slowing down. What are the signs of ω and ?
ω is positive and  is positive.
ω is positive and  is negative.
ω is negative and  is positive.
ω is negative and  is negative.
ω is positive and  is zero.
Answer: C
© 2015 Pearson Education, Inc.

11. QuickCheck 7.5
The fan blade is slowing down. What are the signs of ω and ?
ω is positive and  is positive.
ω is positive and  is negative.
ω is negative and  is positive.
ω is negative and  is negative.
ω is positive and  is zero.
“Slowing down” means that  and  have opposite signs, not that  is negative.
© 2015 Pearson Education, Inc.

12. QuickCheck 7.6
The fan blade is speeding up. What are the signs of  and ?
 is positive and  is positive.
 is positive and  is negative.
 is negative and  is positive.
 is negative and  is negative.
Answer: D
© 2015 Pearson Education, Inc. 12

13. QuickCheck 7.6
The fan blade is speeding up. What are the signs of  and ?
 is positive and  is positive.
 is positive and  is negative.
 is negative and  is positive.
 is negative and  is negative.
© 2015 Pearson Education, Inc. 13

14. QuickCheck 7.7
This is the angular velocity graph of a wheel. How many revolutions does the wheel make in the first 4 s? 1 2 4 6 8
Answer: D
© 2015 Pearson Education, Inc.

15. QuickCheck 7.7
This is the angular velocity graph of a wheel. How many revolutions does the wheel make in the first 4 s? 1 2 4 6 8
 = area under the angular velocity curve
© 2015 Pearson Education, Inc.

16. QuickCheck 7.8
Starting from rest, a wheel with constant angular acceleration spins up to 25 rpm in a time t. What will its angular velocity be after time 2t?
25 rpm
50 rpm
75 rpm
100 rpm
200 rpm
Answer: B
© 2015 Pearson Education, Inc.

17. QuickCheck 7.8
Starting from rest, a wheel with constant angular acceleration spins up to 25 rpm in a time t. What will its angular velocity be after time 2t?
25 rpm
50 rpm
75 rpm
100 rpm
200 rpm
© 2015 Pearson Education, Inc.

18. QuickCheck 7.9
Starting from rest, a wheel with constant angular acceleration turns through an angle of 25 rad in a time t. Through what angle will it have turned after time 2t?
25 rad
50 rad
75 rad
100 rad
200 rad
Answer: D
© 2015 Pearson Education, Inc.

19. QuickCheck 7.9
Starting from rest, a wheel with constant angular acceleration turns through an angle of 25 rad in a time t. Through what angle will it have turned after time 2t?
25 rad
50 rad
75 rad
100 rad
200 rad
© 2015 Pearson Education, Inc.

20. QuickCheck 7.10
The four forces shown have the same strength. Which force would be most effective in opening the door?
Force F1
Force F2
Force F3
Force F4
Either F1 or F3
Answer: A
© 2015 Pearson Education, Inc. 20

21. QuickCheck 7.10
The four forces shown have the same strength. Which force would be most effective in opening the door?
Force F1
Force F2
Force F3
Force F4
Either F1 or F3
Your intuition likely led you to choose F1. The reason is that F1 exerts the largest torque about the hinge.
© 2015 Pearson Education, Inc. 21

22. QuickCheck 7.11
Which third force on the wheel, applied at point P, will make the net torque zero?
Answer: A
© 2015 Pearson Education, Inc. 22

23. QuickCheck 7.11
Which third force on the wheel, applied at point P, will make the net torque zero? A.
© 2015 Pearson Education, Inc. 23

24. QuickCheck 7.12
Which point could be the center of gravity of this L-shaped piece? D. A.
Answer: A B. C.
© 2015 Pearson Education, Inc.

25. QuickCheck 7.12
Which point could be the center of gravity of this L-shaped piece? D. A. B. C.
© 2015 Pearson Education, Inc.