QUIZ 6

Exercises and Problems from Conceptual Physics: Note that answers to odd numbered problems are  listed in the paperback supplement "Practicing Physics."

Ch 8

exercises

1

4

6

30

33

41

47

 

 

 

 

 

 

 

 

problems

 1

2

5

6

10

 

 

 

 

 

 

 

 

 

Ch 9

exercises

 3

4

11

12

14

19

26

28

37

47

51

 

 

problems

1

2

3

5

 

 

 

 

 

 

 

 

Sample Quiz 6

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 Ch. 8

exercises                            

4. Sue's . See fig. 8.2
6. varying linear speed. See fig.  8.2
30. The weight of the  beam acts at the geometric center of the beam.  The torque of the boy = the torque due to the beam  weight :  (lever arm of boy) x (weight of boy) = (lever arm of beam weight) x (beam weight.).. The boy places the pivot at a location so that the above equation is true.  Note that the lever arm of boy = distance  between the pivot and the boy ....Note also that  the lever arm of beam =  distance  between the center of the beam  and the pivot.
33. At the center of the earth. This is like the center of mass of a ring being at the geometric center of the ring. 

 problems

 2. speed = radius x angular speed. angular speed = 6.28/30 s,  where 6.28 = 2 x pi,  where pi = 3.14
6. (a) torque = lever arm x force (b) set (0.25 m) x ( 80 N) = (0.10 m) x ( new force) . Find the new force.
10. See page 151. Use angular momentum = mvr. Find the ratio of (mvr for the earth around the sun)  to (mvr for the moon around the earth.) ie. find ( mvr for the earth around the sun)/(mvr for the moon around the earth.)...Use the Physical Data Table at the back of the book. v = radius x angular speed, where angular speed = 6.28/(time for the orbit)
Background

Actual Picture

 Ch. 9

 exercises

4. force is the same if they have the  same mass: force = mg.

11. Nearer the moon  because the moon  has the smaller mass.
14. The same from Newton's Third Law in Chapter 5. 
19. Your weight would go down if the earth  expanded. Your weight would up of the earth shrunk. See the formula in problem 3 below. d = distance from the surface to the center of the earth. If d increases, then mg decreases.
28. There is a force of gravity on the pencil due to the earth. But you are falling with the pencil, so the pencil hovers. 

problems

 3. mg = GMm/d2  .   Cancel  out the m.

5. mg = GMm/d2 ,   where d = 2x 105 m + earth radius .  Find g.