PHYS1224 – FALL 2004
EXAM 1 – PART 2
TUESDAY’S VERSION
NAME: ___________________________________________________
Instruction:
1)
You must box or underline your final answers on each part of a problem
2)
Cheating will not be tolerated
3)
If you have questions about the wording of any problem, you should ask the
test administrator.
4)
Partial credit will be awarded for correct work.
1.
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(20 pts)
2.
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(20 pts)
3.
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(20 pts)
4.
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(30 pts)
5.
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(15 pts)
6.
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(30 pts)
7.
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(15 pts)
8.
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(20 pts)
9.
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(20 pts)
10.
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(25 pts)
11.
______________________________
(10 pts)
12.
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(15 pts)
Total Part II _________________________
(240 pts)
1.
A small button is placed on a horizontal rotating platform with diameter 0.275 m
and a period of rotation of 0.250 seconds. If coefficient of static friction between
the button and the platform is 0.640, what is the maximum distance that the button
can be placed from the center of the platform without flying off?
o
2.
You are given the following vectors:




A   3m î  4m ĵ - 5m k̂ , B  4m î  2m ĵ , C  3m 225 , D  - 3m î  6m ĵ  3mk̂
A.

Write C in Cartesian form?
B.
 

What is E   2A  B in Cartesian form?
C.
 
Determine A  D
D.
 
Determine A  B
3.
In the figure below, a car is driven at constant speed over a circular hill and then
into a circular valley with the same radius of curvature, 200 m. At the top of the
hill, the normal force on the driver from the car seat is 0 and the mass of the
driver is 70 kg.
200 m
200 m
A.
Draw free-body diagram for the driver at the top of the hill.
B.
What is the speed of the car?
C.
What is the normal force applied by the seat upon the driver when the car passes
the bottom of the valley?
4.
Two blocks of mass 76 kg and 48 kg are connected by a string that passes
over a small frictionless pulley of negligible mass as shown below. Assume that
the 48 kg block is initially traveling down the inclined plane and that the
coefficient of kinetic friction between the surface of 48 kg block and the incline is
0.15 while the 76 kg block is sliding on a frictionless surface.
48 kg
76 kg
50
60
A.
Draw and label free-body diagrams for both masses
B.
Find the acceleration of the 76 kg block
B. (Continued)
C.
Find the tension in the string.
D.
Assuming that the inclines are sufficiently long so that the blocks stay on their
respective sides, how long before the 48 kg block begins sliding up the incline?
5.
In the figure below, a radar station detects an airplane approaching directly from
the east. At first observation, the airplane is at distance d1 = 360 m from the
station and at an angle 1 = 40 above the horizon. The airplane is tracked through
an angular change  = 123 in the vertical east-west plane; its distance is then
d2 = 790 m. Find the airplane’s displacement during this period.
d2

d1
1
6.
In the figure below, a stone is projected at a cliff of height h with an initial speed
of 42.0 m/s directed at an angle o = 60.0 above the horizontal. The stone strikes
at A, 5.50 s after launching.
A
H
h
o
SCRATCH AREA FOR SETTING UP THE PROBLEM
A)
What is the stone’s initial velocity in the vertical direction?
B)
What is the stone’s initial velocity in the horizontal direction?
C)
What is the height of the cliff?
D)
What is speed of the stone just before it hits the cliff?
7.
A ball’s velocity-time graph is shown below,
v (m/s)
12
8
4
t (s)
2
4
6
8
10
A.
Determine the displacement of the ball from t = 4 s to t = 10 s.
B.
Determine the acceleration of the ball at t = 5 s.
C.
Determine the average acceleration of the ball during the first 10 s?
8.
A TSU student lifts a chain consisting of five links, each with a mass of 0.100 kg,
vertically with constant acceleration of magnitude a = 2.50 m/s2.

F
5
4
3
2
1
A.
What is the magnitude of the force on link 1 applied by link 2?
B.
What is the magnitude of the force applied by the TSU student to the top link?
9.
A proton moves along the x axis according to the equation
x  5.0 t 1.0 t 2  2.0 t 3 , where x is in meters and t is in seconds.
A.
Calculate the average velocity of the proton during the first 3.0 s of its motion.
B.
Calculate the velocity of the proton at t = 3.0 s.
C.
Calculate the proton’s acceleration at t=3.0 s.
D.
What is the average acceleration of the proton over the time interval t = 1.0 s to
t = 3.0 s?
10.
Suppose that a man jumps off a building 202 m high onto cushions having a total
thickness of 2 m. If the cushions are crushed to a thickness of 0.5 m, what is the
man’s acceleration as he slows down due to his interaction with the cushions. You
may assume in this problem that air friction is negligible and that the cushions
apply a constant force when slowing down the man.
202 m
2m
11.
Short Answer (5 pts each)
A.
You are driving a classic 1954 Nash Ambassador with a friend who is sitting to
your right on the passenger side of the front seat. You would like to be closer to
your friend and decide to use physics to achieve your romantic goal by making a
quick turn. Explain both type of turn you propose to make and why your friend
will move toward you.
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B. Use Einstein’s equivalence principle to explain how the path of a light beam can be
bent by the gravitational field of a star.
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12.
In lab you drop a ball from a height of 2.0 meters above the floor and measure the
maximum height which the ball obtains following each successive bounce. The
data from the experiment is provided in the table below. Graphically determine
the mathematical equation relating the maximum bounce height to the number of
bounces using the log-log, semi-log, and linear graph paper provided. All
calculations and graphs must be provided for credit. The axis on your graphs must
be labeled. No credit will be given for calculator solutions or guessing.
Bounce
0
1
2
3
Height (meters)
2.00 +/- 0.02
1.58 +/- 0.02
1.28 +/- 0.02
1.02 +/- 0.02
Bounce
4
5
6
7
Height (meters)
0.82 +/- 0.02
0.66 +/- 0.02
0.52 +/- 0.02
0.42 +/- 0.02