Download Old Final exam w06

General Physics – ph 201
Final Exam (Ch 1 – 10)
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Name:____________
Type A
Exam is closed book and closed notes. Use only your note card.
Answer all True/False, Multiple Choice questions and the Problems on
color papers provided.
Show all your work and explain your reasoning for questions and
problems in Part III. No credit will be given for an answer that does not
include the necessary solution or explanation.
Partial credit may be awarded for a correct method of solution, even if the
answer is wrong.
Part I – True or False (5 points each): For questions 1 – 11, state whether each
statement is true or false.
1. The momentum of a heavy object is greater than the momentum of a light object
moving at the same speed.
2. If the angular velocity of an object is zero at some instant, the angular
acceleration of the object must be zero at that instant.
3. The force of gravity does work on a satellite in circular orbit.
4. In the presence of frictional forces, the total mechanical energy always decreases.
5. If kinetic energy is conserved in a collision, then momentum must be conserved.
6. All parts of a rotating wheel must have the same angular velocity.
7. The force of static friction always equals sFN.
8. The equation x = xo + vot + ½at2 is valid for all particle motion in x direction (i.e.
one dimension).
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9. F  r (dot product of force and displacement) is the definition of work.
Part II – Multiple Choice (5 points each): Choose the one correct answer for each of
the following questions that best answers or completes the question.
10. If the net force on a moving object is suddenly reduced to zero, as a consequent
the object
A) stops over a short distance.
D) stops abruptly.
B) continues its motion at constant velocity.
E) changes direction.
C) changes velocity in an unknown way .
11. A block whose weight is 20 N rests on a horizontal surface. The coefficient of
static friction between the block and supporting surface is 1.0. A string is attached
to the block. The tension in the string is 20 N, and the string makes an angle of
30o with the horizontal.
FT = 20 N
A) The block will remain at rest, and fs = 17.3N
30
B) The block will move horizontally.
20 N
s=1.0
C) The block will be lifted off the surface by the string.
D) The block will remain at rest; the force of static friction is less than 17.3 N.
0
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12. A horse pulls a cart with force F. As a result of this force the cart accelerates with
constant acceleration. What is the magnitude of the force that the cart exerts on
the horse?
A) Less than the magnitude of F.
C) Zero.
B) More than the magnitude of F.
D) Equal to the magnitude of F.
13. Complete the following statement: The term net force most accurately describes
A) the mass of an object
B) the inertia of an object.
C) the quantity that causes displacement.
D) the quantity that keeps an object moving.
E) the quantity that changes the velocity of an object.
14. A particle travels along a curved path between two points P and Q as shown. The
displacement of the particle does not depend on
A) the location of P.
B) the location of Q.
C) the distance traveled from P to Q.
D) the shortest distance between P and Q.
E) the direction of Q from P.
15. Two 5-N boxes are attached to opposite ends of a spring scale and suspended
from pulleys as shown. What is the reading on the scale?
A) 0 N
B) 2.5 N
C) 5 N
D) 10 N
E) 25 N
16. Note the following situations: In which case will the magnitude of the normal
force on the block be equal to (Mg + F sin θ)?
A) case 1 only
B) case 2 only
C) both cases 1 and 2
D) both cases 2 and 3
E) cases 1, 2, and 3
17. As the bullet enters the wood block of a ballistic pendulum, which is/are conserved?
A) kinetic energy and momentum
B) kinetic energy but not momentum
C) momentum but not kinetic energy
D) neither kinetic energy nor momentum
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18. Two identical balls A and B are released from the same height above a table. Ball
A falls freely to the desk while ball B follows a curved, frictionless track to the
surface of the desk. Which of the following statements is true about the speeds of
these two balls when they reach the desk?
A) Ball A is moving faster.
B) Ball B is moving faster.
C) Both balls have the same speed.
D) The radius of the curved track is needed to answer this question.
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19. Consider the wheel rotating counterclockwise as seen from above. If the wheel is
speeding up then the direction of the acceleration of point P (at top) is:
P
C)
B)
D)
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Part III – Problems: Please Show your work clearly and completely for each of the
following problems. Partial credit is only given to a work that is shown clearly.
20. (35 points): The figure shown below is a position versus time graph for the
motion of an object along the x axis. Consider the time interval from A to B. (a) Is
the object moving in the positive or negative direction? (b) Is the object speeding
up or slowing down? (c) Is the acceleration of the object positive or negative?
Now consider the time interval from D to E. (d) Is the object moving in the
positive or negative direction? (e) Is the object speeding up or slowing down? (f)
Is the acceleration of the object positive or negative? (g) Finally, answer these
same three questions for the time interval from C to D.
21. A roof tile falls from rest from the top of a building. An observer inside the
building notices that it takes 0.20 second for the tile to pass her window, whose
height is 1.6 m. How far above the top of the building is the roof?
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22. (30 points) The block of mass m sliding without friction along the looped track
shown below is to remain on the track at all times, even at the very top of the loop
of radius r. (a) In terms of the given quantities determine the minimum release
height h if the block is to remain on the track, even at the top of the circle (whose
radius is r). Next, if the actual release height is 2h, calculate (b) the normal force
exerted by the track at the bottom of the loop, (c) the normal force exerted by the
track at the top of the loop, and (d) the normal force exerted by the track after the
block exits the loop onto the flat section (Note: part (b) – (d) can be solved
without the need of part (a).)
23. ((20 points) An 8.0 g bullet is fired into a 250 g block that is initially at rest at the
edge of a table of height 1.0 m. The bullet remains in the block, and after impact
the block lands 2.0 m from the bottom
of the table. Find the initial speed of
the bullet.
24. (30 points) A projectile of mass 3 kg is
fired with an initial speed of 120 m/s at an angle of 30o with the horizontal. At the top
of its trajectory, the projectile explodes into two fragments of masses 1.2 kg and 1.8
kg. The 1.8 kg fragment lands on the ground directly below the point of explosion 3.6
s after the explosion.
A) Draw a diagram showing the velocity vectors for m1 = 3.0 kg (before
explosion), m2 = 1.2 kg, and m3 = 1.8 kg (after explosion).
B) Find the magnitude of the velocity of the 1.2 kg fragment immediately after
the explosion. (Answer: 320 m/s)
C) Find the distance between the point of firing and the point at which the 1:2 kg
fragment strikes the ground.
D) Calculate the kinetic energy of the projectile before and after the explosion.
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