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Instructor(s): Profs. D. Reitze, H. Chan
PHY 2053
PHYSICS DEPARTMENT
Exam 2
Name (print, last first):
April 2, 2009
Signature:
On my honor, I have neither given nor received unauthorized aid on this examination.
YOUR TEST NUMBER IS THE 5-DIGIT NUMBER AT THE TOP OF EACH PAGE.
(1) Code your test number on your answer sheet (use lines 76–80 on the answer sheet for the 5-digit number).
Code your name on your answer sheet. DARKEN CIRCLES COMPLETELY. Code your UFID number on your
answer sheet.
(2) Print your name on this sheet and sign it also.
(3) Do all scratch work anywhere on this exam that you like. There are 2 blank sheets at the end if you need more space.
Circle your answers on the test form. At the end of the test, this exam printout is to be turned in. No credit will
be given without both answer sheet and printout.
(4) Blacken the circle of your intended answer completely, using a #2 pencil or blue or black ink. Do not
make any stray marks or some answers may be counted as incorrect.
(5) The answers are rounded off. Choose the closest to exact. There is no penalty for guessing.
(6) Hand in the answer sheet separately.
Constants:
G = 6.67 × 10−11 N m2 /kg2
g = 9.80 m/s2
1. A ping-pong ball with mass 50 g hits a wall at a speed of 2.0 m/s perpendicular to the surface. It bounces back with
the same speed. Find the magnitude of the average force exerted on the ball by the wall if the ball is in contact with
the wall for 0.20 s.
(1) 1.0 N
(2) 0.50 N
(3) 0.040 N
(4) 0.020 N
(5) 0.10 N
2. A ping-pong ball with mass 50 g hits a wall at a speed of 4.0 m/s perpendicular to the surface. It bounces back with
the same speed. Find the magnitude of the average force exerted on the ball by the wall if the ball is in contact with
the wall for 0.20 s.
(1) 2.0 N
(2) 1.0 N
(3) 0.080 N
(4) 0.040 N
(5) 0.40 N
3. A ping-pong ball with mass 50 g hits a wall at a speed of 7.0 m/s perpendicular to the surface. It bounces back with
the same speed. Find the magnitude of the average force exerted on the ball by the wall if the ball is in contact with
the wall for 0.20 s.
(1) 3.5 N
(2) 1.8 N
(3) 0.14 N
(4) 0.070 N
(5) 1.2 N
4. A 10-g bullet was traveling at 200 m/s when it hit a 2.0-kg ballistic pendulum. After the collision, the bullet remains
stuck in the pendulum. Find the maximum height reached by the pendulum after the collision.
(1) 0.051 m
(2) 0.11 m
(3) 0.52 m
(4) 0.035 m
(5) 0.37 m
5. A 10-g bullet was traveling at 250 m/s when it hit a 2.0-kg ballistic pendulum. After the collision, the bullet remains
stuck in the pendulum. Find the maximum height reached by the pendulum after the collision.
(1) 0.079 m
(2) 0.15 m
(3) 0.75 m
(4) 0.042 m
(5) 0.43 m
6. A 10-g bullet was traveling at 150 m/s when it hit a 2.0-kg ballistic pendulum. After the collision, the bullet remains
stuck in the pendulum. Find the maximum height reached by the pendulum after the collision.
(1) 0.028 m
(2) 0.071 m
(3) 0.24 m
(4) 0.013 m
(5) 0.14 m
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7. The masses of objects A and B are 2.0 kg and 4.0 kg respectively. They travel on a frictionless surface. Object A travels
to the right at 5.0 m/s. Object B travels to the left at 7.0 m/s. The two objects collide in a perfectly inelastic collision.
Find the change in kinetic energy for this system of two objects.
(1) −96 J
(2) −2.7 J
(3) −192 J
(4) −47 J
(5) −21 J
8. The masses of objects A and B are 2.0 kg and 4.0 kg respectively. They travel on a frictionless surface. Object A travels
to the right at 5.0 m/s. Object B travels to the left at 9.0 m/s. The two objects collide in a perfectly inelastic collision.
Find the change in kinetic energy for this system of two objects.
(1) −131 J
(2) −11 J
(3) −263 J
(4) −64 J
(5) −31 J
9. The masses of objects A and B are 2.0 kg and 4.0 kg respectively. They travel on a frictionless surface. Object A travels
to the right at 5.0 m/s. Object B travels to the left at 3.0 m/s. The two objects collide in a perfectly inelastic collision.
Find the change in kinetic energy for this system of two objects.
(1) −43 J
(2) −2.7 J
(3) −85 J
(4) −23 J
(5) −12 J
10. A toy car and a toy truck undergo an elastic head-on collision. The mass of the car is 500 g. The mass of the truck is
900 g. Immediately before the collision, the car traveled at 11.0 mm/s eastwards and the truck traveled at 7.0 mm/s
westwards. Find the speed of the truck immediately after the collision.
(1) 5.9 mm/s
(2) 12.1 mm/s
(3) 0.57 mm/s
(4) 3.1 mm/s
(5) 9.4 mm/s
11. A toy car and a toy truck undergo an elastic head-on collision. The mass of the car is 500 g. The mass of the truck is
1100 g. Immediately before the collision, the car traveled at 11.0 mm/s eastwards and the truck traveled at 7.0 mm/s
westwards. Find the speed of the truck immediately after the collision.
(1) 4.3 mm/s
(2) 13.8 mm/s
(3) 1.4 mm/s
(4) 2.2 mm/s
(5) 9.9 mm/s
12. A toy car and a toy truck undergo an elastic head-on collision. The mass of the car is 500 g. The mass of the truck is
1300 g. Immediately before the collision, the car traveled at 11.0 mm/s eastwards and the truck traveled at 7.0 mm/s
westwards. Find the speed of the truck immediately after the collision.
(1) 3.0 mm/s
(2) 15 mm/s
(3) 2.0 mm/s
(4) 1.2 mm/s
(5) 7.6 mm/s
13. A pendulum consists of a heavy sphere attached to one end of a massless string. The other end of the string is fixed. The
dashed line represents the vertical. Find the direction of the acceleration of the sphere at the highest point (indicated
by arrow).
(1)
(2)
(3)
(4)
(5) —
14. A 0.70 kg object attached to the end of a string of length 0.60 m is swung in a circular path and in a vertical plane. The
angular speed is maintained at 9.0 rad/s. What is the tension in the string when the object is at the top of the circular
path?
(1) 27 N
(2) 41 N
(3) 101 N
(4) 88 N
(5) 34 N
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15. A 0.70 kg object attached to the end of a string of length 0.80 m is swung in a circular path and in a vertical plane. The
angular speed is maintained at 9.0 rad/s. What is the tension in the string when the object is at the top of the circular
path?
(1) 39 N
(2) 52 N
(3) 78 N
(4) 64 N
(5) E. 45 N
16. A 0.70 kg object attached to the end of a string of length 0.60 m is swung in a circular path and in a vertical plane.
The angular speed is maintained at 11.0 rad/s. What is the tension in the string when the object is at the top of the
circular path?
(1) 44 N
(2) 58 N
(3) 148 N
(4) 134 N
(5) 51 N
17. Two ice hockey pucks slide without friction on a flat surface of ice. Puck A (mass = 0.1 kg) traveled at 5.0 m/s eastward
and puck B (mass = 0.2 kg) traveled at 7.0 m/s southward. They collide and remain stuck together. Find the speed
after the collision.
(1) 5.0 m/s
(2) 4.7 m/s
(3) 1.6 m/s
(4) 8.6 m/s
(5) 12 m/s
18. Two ice hockey pucks slide without friction on a flat surface of ice. Puck A (mass = 0.1 kg) traveled at 5.0 m/s eastward
and puck B (mass = 0.3 kg) traveled at 7.0 m/s southward. They collide and remain stuck together. Find the speed
after the collision.
(1) 5.4 m/s
(2) 1.3 m/s
(3) 5.5 m/s
(4) 8.6 m/s
(5) 12 m/s
19. Two ice hockey pucks slide without friction on a flat surface of ice. Puck A (mass = 0.1 kg) traveled at 5.0 m/s eastward
and puck B (mass = 0.05 kg) traveled at 7.0 m/s southward. They collide and remain stuck together. Find the speed
after the collision.
(1) 4.1 m/s
(2) 3.3 m/s
(3) 2.3 m/s
(4) 8.6 m/s
(5) 12 m/s
20. A merry-go-round with radius 5.0 meters starts from rest and undergoes constant angular acceleration of 0.0010 rad/s2 .
After 4 complete revolutions, find the tangential speed at the edge.
(1) 1.1 m/s
(2) 0.22 m/s
(3) 0.65 m/s
(4) 1.5 m/s
(5) 2.3 m/s
21. A merry-go-round with radius 5.0 meters starts from rest and undergoes constant angular acceleration of 0.0010 rad/s2 .
After 3 complete revolutions, find the tangential speed at the edge.
(1) 0.97 m/s
(2) 0.19 m/s
(3) 0.59 m/s
(4) 1.36 m/s
(5) 1.98 m/s
22. A merry-go-round with radius 6.0 meters starts from rest and undergoes constant angular acceleration of 0.0010 rad/s2 .
After 4 complete revolutions, find the tangential speed at the edge.
(1) 1.3 m/s
(2) 0.22 m/s
(3) 0.65 m/s
(4) 1.7 m/s
(5) 2.3 m/s
23. The gravitational force exerted on an astronaut on Earth’s surface is 700 N. She was transported by a space shuttle to
a space station at distance 2rE from the earth surface (where rE is the radius of the Earth). What is the gravitation
force on the astronaut at the space station?
(1) 77.8 N
(2) 175 N
(3) 350 N
(4) 233 N
(5) 1400 N
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24. The gravitational force exerted on an astronaut on Earth’s surface is 500 N. She was transported by a space shuttle to
a space station at distance 2rE from the earth surface (where rE is the radius of the Earth). What is the gravitation
force on the astronaut at the space station?
(1) 55.6 N
(2) 125 N
(3) 250 N
(4) 167 N
(5) 1000 N
25. The gravitational force exerted on an astronaut on Earth’s surface is 600 N. She was transported by a space shuttle to
a space station at distance 2rE from the earth surface (where rE is the radius of the Earth). What is the gravitation
force on the astronaut at the space station?
(1) 66.7 N
(2) 150 N
(3) 300 N
(4) 200 N
(5) 1200 N
26. A 500 kg elevator starts from rest and moves upward for 4.00 s with a constant acceleration until it reaches a velocity
of 2.50 m/s. What is the average power of the elevator during this period?
(1) 6520 W
(2) 390 W
(3) 1280 W
(4) 790 W
(5) 3230 W
27. A 600 kg elevator starts from rest and moves upward for 3.00 s with a constant acceleration until it reaches a velocity
of 2.50 m/s. What is the average power of the elevator during this period?
(1) 8000 W
(2) 900 W
(3) 4510 W
(4) 5540 W
(5) 280 W
28. A 800 kg elevator starts from rest and moves upward for 4.00 s with a constant acceleration until it reaches a velocity
of 1.50 m/s. What is the average power of the elevator during this period?
(1) 6110 W
(2) 230 W
(3) 3020 W
(4) 490 W
(5) 10900 W
29. A 0.6 kg block is pressed against a spring (k = 300 N/m), compressing the spring by 4.3 cm. The block is released. It
first travels on a frictionless track and then up a θ = 45◦ inclined plane. How high (vertically) does the block rise above
the track?
(1) 4.7 cm
(2) 10.4 cm
(3) 1.2 cm
(4) 21.2 cm
(5) not enough information given to solve the problem
30. A 0.3 kg block is pressed against a spring (k = 500 N/m), compressing the spring by 5.1 cm. The block is released. It
first travels on a frictionless track and then up a θ = 45◦ inclined plane. How high (vertically) does the block rise above
the track?
(1) 22.1 cm
(2) 14.9 cm
(3) 4.2 cm
(4) 1.7 cm
(5) not enough information given to solve the problem
31. A 0.4 kg block is pressed against a spring (k = 100 N/m), compressing the spring by 10.8 cm. The block is released. It
first travels on a frictionless track and then up a θ = 45◦ inclined plane. How high (vertically) does the block rise above
the track?
(1) 14.9 cm
(2) 6.2 cm
(3) 34.3 cm
(4) 12.0 cm
(5) not enough information given to solve the problem
32. Three rigid objects, a solid cylinder (I = (1/2)M R2 ), a hoop (I = M R2 ), and solid sphere (I = (2/5)M R2 ) have the
same mass, radius, and angular speed about their central axis. If the same braking torque is applied to each object,
which object takes the longest to stop?
(1)
(2)
(3)
(4)
(5)
the hoop
the solid cylinder
the solid sphere
they all come to rest at the same time
not enough information given
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33. A dumbbell is made of two masses (m = 10.0 kg) connected together
by a rigid massless rod (length L = 0.40 m). The dumbbell rotates
on an axis perpendicular to the page through the midpoint as shown.
Forces F1 = 100 N and F2 = 40 N are exerted on the masses as shown.
If the dumbbell starts from rest, what is the angular speed after 3 s?
(1) 45 rad/s
(2) 15 rad/s
(3) 25 rad/s
(4) 75 rad/s
(5) 10 rad/s
(4) 25.0 rad/s
(5) 3.2 rad/s
34. A dumbbell is made of two masses (m = 8.0 kg) connected together by
a rigid massless rod (length L = 0.60 m). The dumbbell rotates on an
axis perpendicular to the page through the midpoint as shown. Forces
F1 = 70 N and F2 = 60 N are exerted on the masses as shown. If the
dumbbell starts from rest, what is the angular speed after 3 s?
(1) 6.3 rad/s
(2) 12.5 rad/s
(3) 2.4 rad/s
35. A dumbbell is made of two masses (m = 3.0 kg) connected together by
a rigid massless rod (length L = 1.40 m). The dumbbell rotates on an
axis perpendicular to the page through the midpoint as shown. Forces
F1 = 50 N and F2 = 20 N are exerted on the masses as shown. If the
dumbbell starts from rest, what is the angular speed after 3 s?
(1) 21.4 rad/s
(2) 32.1 rad/s
(3) 12.9 rad/s
(4) 25.0 rad/s
(5) 6.3 rad/s
36. An ice skater is initially spinning with her arms extended away from her body. Her angular velocity is 6.0 rad/s and her
moment of inertia is 12 kg m2 . When she pulls her arms in, her moment of inertia decreases to 8.0 kg m2 . What is her
final rotational kinetic energy?
(1) 320 J
(2) 180 J
(3) 540 J
(4) 420 J
(5) 210 J
37. An ice skater is initially spinning with her arms extended away from her body. Her angular velocity is 5.0 rad/s and her
moment of inertia is 15 kg m2 . When she pulls her arms in, her moment of inertia decreases to 9 kg m2 . What is her
final rotational kinetic energy?
(1) 310 J
(2) 110 J
(3) 45 J
(4) 540 J
(5) 220 J
38. An ice skater is initially spinning with her arms extended away from her body. Her angular velocity is 6.0 rad/s and her
moment of inertia is 13 kg m2 . When she pulls in her arms, her moment of inertia decreases to 7 kg m2 . What is her
final rotational kinetic energy?
(1) 430 J
(2) 210 J
(3) 100 J
(4) 55 J
(5) 35 J
(4) 85 N
(5) 780 N
39. A uniform beam of mass m1 = 20 kg and length L = 2.0 m extends
out from the wall as shown. A mass m2 = 10 kg hangs from its end.
The beam is supported by a cable that makes an angle of θ = 45◦ with
the beam. The system is in equilibrium. What is the tension in the
cable?
(1) 280 N
(2) 140 N
(3) 370 N
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40. A uniform 15 kg beam of length 2 m extends out from the wall as
shown. A 20 kg mass hangs from its end. The beam is supported by a
cable that makes an angle of θ = 45◦ with the beam. The system is in
equilibrium. What is the tension in the cable?
(1) 380 N
(2) 230 N
(3) 95 N
(4) 820 N
(5) 780 N
(4) 940 N
(5) 320 N
41. A uniform 25 kg beam of length 2 m extends out from the wall as
shown. A 30 kg mass hangs from its end. The beam is supported by a
cable that makes an angle of θ = 45◦ with the beam. The system is in
equilibrium. What is the tension in the cable?
(1) 590 N
(2) 430 N
(3) 75 N
42. An isolated object with a rotational kinetic energy of 120 J and a moment of inertia equal to 120 kg m2 . What is its
angular momentum?
(1) 170 kg m2 / s
(2) 95 kg m2 / s
(3) 250 kg m2 / s
(4) 410 kg m2 / s
(5) 63 kg m2 / s
43. An isolated object with a rotational kinetic energy of 140 J and a moment of inertia equal to 80 kg m2 . What is its
angular momentum?
(1) 150 kg m2 / s
(2) 48 kg m2 / s
(3) 320 kg m2 / s
(4) 270 kg m2 / s
(5) 76 kg m2 / s
44. An isolated object with a rotational kinetic energy of 220 J and a moment of inertia equal to 20 kg m2 . What is its
angular momentum?
(1) 94 kg m2 / s
(2) 140 kg m2 / s
(3) 34 kg m2 / s
(4) 320 kg m2 / s
(5) 250 kg m2 / s
45. An ice skater is spinning with her hands extended outward from her body. When she pulls her arms in, she spins with
a different angular speed. Which quantity (quantities) below is (are) conserved?
(1)
(2)
(3)
(4)
(5)
Angular momentum
Rotational kinetic energy
Angular momentum and rotational kinetic energy
Neither angular momentum nor rotational kinetic energy are conserved
Not enough information is given to answer this question.
46. A solid cylinder (moment of inertia I = (1/2)M R2 ) starts from rest at the top of an inclined plane and rolls down
without slipping. If the inclined plane is 1.0 m high, what is the speed of the cylinder when it reaches the bottom of the
inclined plane?
(1) 3.6 m/s
(2) 4.4 m/s
(3) 2.1 m/s
(4) 9.8 m/s
(5) 7.6 m/s
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47. A solid cylinder (moment of inertia I = (1/2)M R2 ) starts from rest at the top of an inclined plane and rolls down
without slipping. If the inclined plane is 1.5 m high, what is the speed of the cylinder when it reaches the bottom of the
inclined plane?
(1) 4.4 m/s
(2) 5.4 m/s
(3) 8.8 m/s
(4) 2.8 m/s
(5) 2.1 m/s
48. A solid cylinder (moment of inertia I = (1/2)M R2 ) starts from rest at the top of an inclined plane and rolls down
without slipping. If the inclined plane is 1.2 m high, what is the speed of the cylinder when it reaches the bottom of the
inclined plane?
(1) 4.0 m/s
(2) 4.8 m/s
(3) 1.3 m/s
(4) 7.9 m/s
(5) 2.0 m/s
(4) 3.6 m/s2
(5) 1.5 m/s2
(4) 7.2 m/s2
(5) 1.2 m/s2
(4) 5.1 m/s2
(5) 2.1 m/s2
49. In the figure, m1 = 20 kg, m2 = 35 kg, and the pulley is a solid
cylinder with mass M = 25.0 kg, radius R = 0.30 m and moment
of inertia I = (1/2)M R2 . The masses begin at rest, and then start
to move, with the heavier mass accelerating downward and light mass
accelerating upward. The rope applies a torque to the pulley, rotating
the pulley about a frictionless axle. Find the acceleration.
(1) 2.2 m/s2
(2) 9.8 m/s2
(3) 2.8 m/s2
50. In the figure below, m1 = 15 kg, m2 = 55 kg, and the pulley is a
solid cylinder with mass M = 10.0 kg, radius R = 0.30 m and moment
of inertia I = (1/2)M R2 . The masses begin at rest, and then start
to move, with the heavier mass accelerating downward and light mass
accelerating upward. The rope applies a torque to the pulley, rotating
the pulley about a frictionless axle. Find the acceleration.
(1) 5.2 m/s2
(2) 9.8 m/s2
(3) 3.1 m/s2
51. In the figure below, m1 = 10 kg, m2 = 15 kg, and the pulley is a
solid cylinder with mass M = 20.0 kg, radius R = 0.30 m and moment
of inertia I = (1/2)M R2 . The masses begin at rest, and then start
to move, with the heavier mass accelerating downward and light mass
accelerating upward. The rope applies a torque to the pulley, rotating
the pulley about a frictionless axle. Find the acceleration.
(1) 1.4 m/s2
(2) 9.8 m/s2
(3) 2.8 m/s2
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52. In order to receive credit for this problem, you must correctly code (“bubble in”) your UFID and your 5-digit test number
(located at the top left and right hand corners of this test) onto your scan sheet and also select the correct response
below. Please check now that you have correctly coded your exam number on the scan sheet.
(1)
(2)
(3)
(4)
(5)
I have correctly bubbled my UFID number and 5-digit test code.
I won’t do this because I don’t need the credit.
I don’t know what my UFID number is.
If I don’t pick the answer that was stated in class, will I still get credit?
I don’t understand what is being asked.
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