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SHORT ANSWER [37 points] Only the answer will be graded. You do not need to show
any work. For multiple choice, please mark
letters
of your answers in spaces provided.
1.
[3 points]
A team of P112 students is bouncing
a beach ball [of mass m=0.200 kg] in the lab, taking
position data with a sonar ranger. Their computer
calculates a graph of velocity versus time. They
analyze this graph for the time interval between the
first two bounces. For illustration, the graph is shown
here.
The velocity and slope of the
vt
graph at the three
marked points are:
(1)
ball rising
v
= 2.0 m/s slope =
a
1
=  8.1 m/s
2
(2)
v
= 0
slope =
a
2
=  7.2 m/s
2
(3)
ball falling
v
=  2.0 m/s slope =
a
3
=  6.4 m/s
2
Based on these data, what is the
direction
of the
sum of all forces other than gravity,
F
other
→
, at times
(1), (2), and (3)? In the spaces below mark the letter corresponding to the direction.
(A)
(E)
(F)
F
other
→
=0
(a)
At time (1) the direction of
F
other
→
corresponds to letter ___________
(b)
At time (2) the direction of
F
other
→
corresponds to letter ___________
(c)
At time (3) the direction of
F
other
→
corresponds to letter ___________
2.
[5 points]
Using the data from question #1, calculate the magnitude of the
air drag
force
acting on the ball at point #1.
Answer: ________________ N
0
t
v (t)
y
1
2
3
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2
3.
[6 points]
A Hand pushes horizontally on block
A. Block A is stacked on top of block B, which sits on
a level floor. There is friction between each surface.
Block B moves to the right (
→
) with
constant velocity
.
Block A is accelerating to the right (
→
).
(a)
How does the magnitude of the
friction force
due to B on A compare with the
magnitude of the
friction force
due to A on B?
(A)
f
B on A
> f
A on B
(B)
f
B on A
< f
A on B
(C)
f
B on A
= f
A on B
(D)
This can't be determined here.
Answer:
(b)
How does the magnitude of the
friction force
due to A on B compare with the
magnitude of the
friction force
due to the floor on B?
(A)
f
Floor on B
> f
A on B
(B)
f
Floor on B
< f
A on B
(C)
f
Floor on B
= f
A on B
(D)
This can't be determined here.
Answer:
(c)
Which arrow best describes the direction of the
friction force
due to A on B?
(A)
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 Spring '07
 LECLAIR,A
 Mass, Work

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