Physics 101.
Last Name:
Discussion Section:
Hour Exam 2
First Name
Discussion TA Name:
Summer 2013
Net ID:
Instructions—
Turn off your cell phone and put it away.
This is a closed book exam. You have sixty (60) minutes to complete it.
1. Use a #2 pencil; do not use a mechanical pencil or a pen. Fill in completely (until
there is no white space visible) the circle for each intended input – both on the
identification side of your answer sheet and on the side on which you mark your answers.
If you decide to change an answer, erase vigorously; the scanner sometimes registers
incompletely erased marks as intended answers; this can adversely affect your grade.
Light marks or marks extending outside the circle may be read improperly by the
scanner.
2. Print your last name in the YOUR LAST NAME boxes on your answer sheet and
print the first letter of your first name in the FIRST NAME INI box. Mark (as described
above) the corresponding circle below each of these letters.
3. Print your NetID in the NETWORK ID boxes, and then mark the corresponding
circle below each of the letters or numerals. Note that there are different circles for the
letter “I” and the numeral “1” and for the letter “O” and the numeral “0”. Do not mark
the hyphen circle at the bottom of any of these columns.
4. This Exam Booklet is Version A. Mark the A circle in the TEST FORM box at the
bottom of the front side of your answer sheet.
5. Stop now and double-check that you have bubbled-in all the information requested in
2 through 4 above and that your marks meet the criteria in 1 above. Check that you do
not have more than one circle marked in any of the columns.
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the COURSE or INSTRUCTOR lines.)
8. Sign (DO NOT PRINT) your name on the STUDENT SIGNATURE line.
Before starting work, check to make sure that your test booklet is complete. You should
have 9 numbered pages including the Formula Sheets.
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student or using unauthorized materials during a University Examination can be
grounds for disciplinary action, up to and including expulsion.
Page 1 of 9
(23 problems)
Physics 101.
Hour Exam 2
Summer 2013
Exam Grading Policy—
The exam is worth a total of 111 points, and is composed of three types of questions.
MC5: multiple-choice-five-answer questions, each worth 6 points.
Partial credit will be granted as follows.
((A) If you mark only one answer and it is the correct answer,
you earn 6 points.
(b) If you mark two answers, one of which is the correct answer,
you earn 3 points.
(c) If you mark three answers, one of which is the correct answer,
you earn 2 points.
(d) If you mark no answers, or more than three, you earn 0 points.
MC3: multiple-choice-three-answer questions, each worth 3 points.
No partial credit.
((A) If you mark only one answer and it is the correct answer,
you earn 3 points.
(b) If you mark a wrong answer or no answers, you earn 0 points.
TF: true-false questions, each worth 2 points.
No partial credit.
((A) If you mark only one answer and it is the correct answer,
you earn 2 points.
(b) If you mark the wrong answer or neither answer, you earn 0 points.
You should assume that the acceleration of gravity near the surface of the earth is 9.8 m/s2
downward, and ignore any effects due to air resistance.
Page 2 of 9 pages
(23 problems)
Physics 101.
Hour Exam 2
Summer 2013
1. Two masses are hung over a massless pulley as shown. The left mass is m1 = 10 kg and the right
mass is m2 = 4 kg. Both masses begin h = 2.3 m off the ground. Initially both blocks are at rest.
h
The blocks are released, how fast is the left block moving right before it hits the ground?
(A)
(B)
(C)
(D)
(E)
1.5 m/s
2.1 m/s
3.7 m/s
4.4 m/s
5.1 m/s
2. A block of mass M = 2kg and velocity V = 5 m/s is moving on a horizontal frictionless surface.
The block collides and sticks together with another identical block of M = 2kg initially at rest.
Those two blocks collide and stick together with a third identical block initially at rest and all three
blocks collide with and stick to a fourth identical block initially at rest. What is the final momentum
of all four blocks?
(A) 2 kg*m/s
(B) 5 kg*m/s
(C) 10 kg*m/s
3. The driver of an empty speeding truck slams on the brakes and skids to a stop in a distance D. If
the truck were carrying a load that doubled its mass, what would its stopping distance have been?
(Assume the road is straight and horizontal and that the coefficient of kinetic friction is constant).
(A) D
(B) 2D
(C) 4D
4. A car starts from rest and accelerates uniformly to a speed of 30 m/s. During this acceleration the
car travels a distance of 250 m. How many revolutions has each of the tires on the car traveled.
The radius of each tire is 0.4 m. (The wheels never skid on the pavement.)
(A) 55.2
(B) 71.3
(C) 99.5
Page 3 of 9 pages
(23 problems)
Physics 101.
Hour Exam 2
Summer 2013
The next four questions are about the following situation:
A block (starting from rest) with mass m = 4.5 kg slides down a frictionless incline with a vertical
height of h = 2 m and then slides across a horizontal floor with friction (the coefficient of kinetic
friction is  = 0.4).
m
h
5. What is the speed of the block at the bottom of the incline?
(A)
(B)
(C)
(D)
(E)
3.56 m/s
4.79 m/s
5.67 m/s
6.26 m/s
9.02 m/s
6. What is the magnitude of the work done by friction in bringing the block to rest?
(A)
(B)
(C)
(D)
(E)
65.8 J
88.2 J
132 J
179 J
202 J
7. What is the speed of the block after it has traveled a distance of 2m on the horizontal floor? (The
2m does not include the incline)
(A)
(B)
(C)
(D)
(E)
3.56 m/s
4.85 m/s
5.67 m/s
7.67 m/s
9.02 m/s
8. How would the magnitude of the work done by gravity on the way down the incline change if the
mass were doubled?
(A) it would stay the same
(B) it would be greater than before
(C) it would be less than before
Page 4 of 9 pages
(23 problems)
Physics 101.
Hour Exam 2
Summer 2013
The next two questions are about the following situation:
A golf ball is fired at a bowling ball, which is initially at rest and bounces back will half its initial
speed but in the opposite direction. The bowling ball has a mass 100 times greater than the golf ball.
After the collision both balls are moving in opposite directions.
9. Compare the magnitude of the final momentum of the golf ball, pg, to the magnitude of the final
momentum of the bowling ball, pb.
(A) |pg| < |pb|
(B) |pg| = |pb|
(C) |pg| > |pb|
10. Compare the final Kinetic Energy of the golf ball, KEg, to the final Kinetic Energy of the
bowling ball, KEb.
(A) KEg < KEb
(B) KEg = KEb
(C) KEg > KEb
This and the next problem are about the following situation:
11. A wheel with a radius of 0.2 m is initially at rest and undergoes an angular acceleration of  = 4
rad/sec2 for 20 seconds, after 20 seconds it continues to rotate at a constant angular velocity. What is
the final speed of a point on the outer rim of the wheel?
(A)
(B)
(C)
(D)
(E)
7.5 m/s
11 m/s
16 m/s
23 m/s
29 m/s
12. How long, from rest, does it take for the wheel to travel through 250 revolutions?
(A)
(B)
(C)
(D)
(E)
17.3 s
21.1 s
22.8 s
25.3 s
29.6 s
Page 5 of 9 pages
(23 problems)
Physics 101.
Hour Exam 2
Summer 2013
The next three questions are about the following situation:
A potato gun works by igniting a flammable substance in a sealed chamber, which builds pressure in
the chamber. Assume this pressure applies a constant force on the potato while it is in the barrel of
the gun. (Each potato has the same force applied to it over the distance, L, of the barrel.)
Potato
F
L
You fire two potatoes out of the potato gun. Both potatoes have the same size and shape, but Potato
A has a larger mass than Potato B, mA>mB.
13. Which potato will have the greatest velocity when leaving the barrel?
(A) Potato A
(B) Potato B
(C) They will have the same velocity.
14. Which potato will have the greatest kinetic energy when leaving the barrel?
(A) Potato A
(B) Potato B
(C) They will have the same kinetic energy.
15. Which potato will have the greatest momentum when leaving the barrel?
(A) Potato A
(B) Potato B
(C) They will have the same momentum.
Page 6 of 9 pages
(23 problems)
Physics 101.
Hour Exam 2
The next four questions pertain to the following situation.
Summer 2013
R
At an amusement park, some physics students are on
a ride where they stand against the wall in a cylindrical
apparatus that begins to rotate around its center.
Once they are moving fast enough the floor drops and
they “stick” to the wall due to friction. Consider one
particular student with a mass of 80 kg. The radius
of the cylinder is R = 3 m and the minimum speed the
ride must move the people at to keep them from sliding
down the wall is 10m/s.
16. What is the direction of the force of friction on the student?
(A)
(B)
(C)
(D)
(E)
up
down
inward toward the center
outward away from the center
the frictional force is zero
17. What is the direction of the normal force on the student?
(A)
(B)
(C)
(D)
(E)
up
down
inward toward the center
outward away from the center
the normal force is zero
18. What is the centripetal acceleration of the student?
(A)
(B)
(C)
(D)
(E)
11.5 m/s2
13.1 m/s2
26.1 m/s2
30.2 m/s2
33.3 m/s2
19. What is the coefficient of static friction between the student and wall?
(A)
(B)
(C)
(D)
(E)
0.3
0.4
0.5
0.6
0.7
Page 7 of 9 pages
(23 problems)
Physics 101.
Hour Exam 2
Summer 2013
The next four questions are about the following situation:
A block moving with speed vo = 5 m/s and mass m1 = 10 kg collides with a block of mass m2 = 8 kg
initially at rest. Both slide on a frictionless surface at all times.
vo
m1
m2
20. If the two blocks stick together, what is their final speed?
(A)
(B)
(C)
(D)
(E)
0.2 m/s
0.6 m/s
1.2 m/s
1.5 m/s
2.8 m/s
21. If the two blocks stick together, how much kinetic energy is lost during the collision?
(A)
(B)
(C)
(D)
(E)
0J
56 J
78 J
92 J
105 J
22. If instead the first block bounces back with a speed of 3 m/s, what is the final speed of the
second block?
(A)
(B)
(C)
(D)
(E)
1.2 m/s
3.4 m/s
5.6 m/s
8.8 m/s
10 m/s
23. Return to the first collision (where the blocks stick together). Now the two blocks collide with a
third block initially at rest. What is the final momentum of the system of three blocks?
(A)
(B)
(C)
(D)
(E)
34 kg-m/s
50 kg-m/s
90 kg-m/s
150 kg-m/s
210 kg-m/s
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Page 8 of 9 pages
(23 problems)
Physics 101.
Hour Exam 2
Summer 2013
Page 9 of 9 pages
(23 problems)