WebAssign
Ch. 8 ­ Regular Physics (Homework)
Current Score : 23.85 / 40
THOMAS FOWLER
Physics, section T1_P5_Carlson,
Instructor: Sarah Carlson
Due : Monday, October 3 2011 11:00 PM MDT
1. –/1.9 points
GPhys09 8.AC.063.
What does a spin cycle of a washing machine do? Explain in terms of the forces on the clothes and water.
2. 1.9/1.9 points | Previous Answers
GPhys09 8.MC.048.
A bicycle wheel rotates at a constant 30 rev/min. Is its angular velocity decreasing, increasing, or constant?
decreasing
increasing constant
3. 1.9/1.9 points | Previous Answers
GPhys09 8.MC.050.
Do all parts of Earth rotate at the same rate? Yes
No Explain
because they all rotate the same amount of degrees during a givin time
4. 1.9/1.9 points | Previous Answers
GPhys09 8.MC.054.
Rank the torques on the five doors shown below from least to greatest. Note that the magnitude of all the forces
is the same.
A
A
A
A
A
B B B B B C
<
C
<
C
<
C
<
C
D
D
D
D
D
E
E
E
E
E
5. 1.9/1.9 points | Previous Answers
GPhys09 8.MP.082.
What is the torque on a bolt produced by a F = 13 N force exerted perpendicular to a wrench that is l = 22 cm
long, as shown below? 2.86
N ∙ m
6. 1.9/1.9 points | Previous Answers
GPhys09 8.MP.086.
A 29.5­kg board, 4.00 m long, is being help up on one end by Ahmed. He calls for help, and Judi responds.
(a) What is the least force that Judi could exert to lift the board to the horizontal position?
144.69
N
What part of the board should she lift to exert this force?
At the opposite end of Ahmed
(b) What is the greatest force that Judi could exert to lift the board to the horizontal position?
289.38
N
What part of the board should she lift to exert this force?
At the middle of the board
7. –/1.9 points
GPhys09 8.MR.090.
Ten bags of top soil, each weighing 185 N, are placed on a 2.50­m long sheet of wood. They are stacked 0.50 m
from one end of the sheet of wood, as shown below. Two people lift the sheet of wood, one at each end. Ignore
the weight of the wood, how much force must each person exert? FLeft person = FRight person = N N 8. 0.95/1.9 points | Previous Answers
GPhys09 8.TC.105.
Gerald and Evelyn carry the following objects up a flight of stairs: a large mirror, a dresser, and a television.
Evelyn is at the front end, and Gerald is at the bottom end. Assume that both Evelyn and Gerald exert only
upward forces.
(a) Draw a free­body diagram showing Gerald and Evelyn exerting the same force on the mirror. (Do this
on paper. Your instructor may ask you to turn in this work.) (b) Draw a free­body diagram showing Gerald exerting more force on the bottom of the dresser.(Do this
on paper. Your instructor may ask you to turn in this work.) (c) Where would the center of mass of the television have to be so that Gerald carries all the weigh? to the left of him
to the right of him directly above him
9. 1.9/1.9 points | Previous Answers
GPhys09 7.AC.040.
Decide whether each of the orbits shown below is a possible orbit for a planet. (The diagram shows a view from
directly above.)
(a)
Yes
No (b)
Yes
No (c)
Yes
No (d)
Yes
No 10. 1.9/1.9 points | Previous Answers
GPhys09 7.AC.042.
What would happen to the value of G if Earth were twice as massive, but remained the same size?
G would be quadrupled
nothing G would be doubled
G would be halved
11. 1.9/1.9 points | Previous Answers
GPhys09 7.MC.028.
What happens to the gravitational force between two masses when the distance between the masses is doubled?
The force is doubled.
The force is unchanged. The force is quartered.
The force is halved.
12. –/1.9 points
GPhys09 8.MP.078.
A washing machine's two spin cycles are 355 rev/min and 500 rev/min. The diameter of the drum is 0.43 m.
(a) What is the ratio of the centripetal accelerations for the fast and slow spin cycles?
afast/aslow = (b) What is the ratio of the linear velocity of an object at the surface of the drum for the fast and slow
spin cycles? vfast/vslow = 13. 1.9/1.9 points | Previous Answers
GPhys09 7.MC.032.
What provides the force that causes the centripetal acceleration of a satellite in orbit?
mass
gravity magnetism
velocity
14. –/1.9 points
GPhys09 7.MP.053.
The figure below shows a Cavendish apparatus like the one used to find G. It has a large lead sphere that is
m1 = 5.9 kg in mass and a small sphere with a mass of m2 = 0.044 kg. Their centers are separated by 0.055 m.
Find the force of attraction between them. (Use G = 6.67 10­11 N ∙ m2/kg2.) N
15. –/1.9 points
GPhys09 7.MP.055.
Tom has a mass of 69.0 kg and Sally has a mass of 55.0 kg. Tom and Sally are standing 20.0 m apart on the
dance floor. Sally looks up and sees Tom. She feels an attraction. If the attraction is gravitational, find its size.
Assume that both Tom and Sally can be replaced by spherical masses. (Use G = 6.67 10­11 N ∙ m2/kg2.)
N
16. –/1.9 points
GPhys09 7.MP.057.
Two bowling balls each have a mass of 6.4 kg. They are located next to each other with their centers 20.6 cm
apart. What gravitational force do they exert on each other? (Use G = 6.67 10­11 N ∙ m2/kg2.)
N
17. –/1.9 points
GPhys09 6.AC.041.
A batter hits a pop­up straight up over home plate at an initial velocity of 16 m/s. The ball is caught by the catcher
at the same height that it was hit. At what velocity does the ball land in the catcher's mitt? Neglect air resistance.
(Take the positive direction to be upwards.)
m/s
18. –/1.9 points
GPhys09 6.AC.045.
A quarterback throws a football at 25 m/s at a certain angle above the horizontal. If it took the ball 3.4 s to reach
the top of its path, how long was it in the air? s
19. 1.9/1.9 points | Previous Answers
GPhys09 6.AC.047.
Imagine that you are sitting in a car tossing a ball straight up into the air.
(a) If the car is moving at constant velocity, will the ball land in front of, behind, or in your hand?
The ball will land in front of your hand.
The ball will land in your hand. The ball will land behind your hand.
(b) If the car rounds a curve at constant speed, where will the ball land?
The ball will land beside you, toward the inside of the curve.
The ball will land in your hand. The ball will land beside you, toward the outside of the curve.
The ball will land behind your hand.
20. 1.9/1.9 points | Previous Answers
GPhys09 6.CR.092.
Plot the data in the table below on a position­time graph. (Do this on paper. Your instructor may ask you to turn in
this graph.)
Find the average velocity in the time interval between 0.0 s and 3.0 s. 5
m/s
21. 2/2 points | Previous Answers
GPhys09 6.MC.036.
(a) Can you go around a curve with zero acceleration?
Yes
No Explain.
acceleration is a change in direction or speed
(b) Can you go around a curve with constant acceleration?
Yes
No Explain.
you are changing your direction during the curve