E.
Circular Motion Take Home Quiz
300
points (15 points/question)
50. A
flywheel, of radius 1 m, is spinning with a constant angular velocity of 2 rad/s.
What is the centripetal acceleration of a point on the wheel's rim?
a. 1m/s2
b. 2 m/s2
c. 4 m/s2
d. None of the above
51. A
fan blade, whose diameter is 1 m, is turning with an angular velocity of 2 rad/s.
What is the tangential velocity of a point on the tip of the blade?
a. 2 m/s
b. 0.5 m/s
c. 1 m/s
d. None of the above
52. What
is the angular speed of a record that rotates at 33-1/3 rpm? (Hint: Convert
33 1/3 RPM into radians. Remember
that RPM means rotations/minute)
a. 33.3/p
rad/s
b. 1.74 rad/s
c. 2.77 rad/s
d. 3.49 rad/s
53. The
banking angle in a turn on the Olympic bobsled track is not constant, but
increases upward from the horizontal. Coming
around a turn, the bobsled team will intentionally "climb the wall,"
then go lower coming out of the turn. Why
do they do this?
a. To give the team better control,
because they are able to see ahead of the turn.
b. To prevent the bobsled from
turning over.
c. To take the turn at a faster
speed.
d. To reduce the g-force on them.
54. A
horizontal curve on a bobsled run is banked at a 45ø angle.
When a bobsled rounds this curve at the curve's safe speed (no friction
needed to stay on the run), what is its centripetal acceleration?
a. 1.0 g
b. 2.0 g
c. 0.5 g
d. None of the above
55. Does
the centripetal force acting on an object do work on the object?
a. Yes, since a force acts and the
object moves, and work is force times distance.
b. Yes, since it takes energy to
turn an object.
c. No, because the object has
constant speed.
d. No, because the force and the
displacement of the object are perpendicular.
56. A
roller coaster car is on a track that forms a circular loop in the vertical
plane. If the car is to just
maintain contact with track at the top of the loop, what is the minimum value
for its centripetal acceleration at this point?
a. g downward
b. 0.5 g downward
c. g upward
d. 2 g upward
57. A
roller coaster car (mass = M) is on a track that forms a circular loop (radius =
r) in the vertical plane. If the
car is to just maintain contact with the track at the top of the loop, what is
the minimum value for its speed at that point?
a.
2 Mrg
b.
c.
d.
None of the above
58. The
speed needed at the bottom of a loop-the-loop track so that a car can coast to
the top, with sufficient speed to stay on the track, depends on the mass of the
car. (Neglect the effects of
friction.)
a. Always true.
b. Never true.
c. Sometimes true, since kinetic
energy is a function of mass.
d. Sometimes true, since potential
energy is a function of mass.
59. The
net force on an object in orbit is zero.
a. True
b. False
60. A
planet revolves clockwise around a star, with constant speed.
The direction of its acceleration at point P is
a. graph A
b. graph B
c. graph C
d. graph D
61. A
girl attaches a rock to a string, which she then swings counter-clockwise in a
horizontal circle. The string
breaks at point P on the sketch, which shows a bird's-eye view (i.e., as seen
from above). What path will the
rock follow?
a. A
b. B
c. C
d. D
e. E
62. Marilyn
(M) and her sister Sheila (S) are riding on a merry-go-round, as shown
(bird's-eye view).
a. They have the same speed, but
their angular velocity is different.
b. They have different speeds, and
different angular velocities.
c. They have different speeds, but
the same angular velocity.
d. They have the same speed and the
same angular velocity.
63. The record playing on the turntable of your stereo is rotating clockwise (as seen from above). After turning it off, your turntable is slowing down, but hasn't stopped yet. The direction of the acceleration of point P (at the left) is: (Hint: It is slowing down! What does that do to its net direction of acceleration). Choose the correct vector arrow above.
64. What
condition or conditions are necessary for rotational equilibrium?
a. SFx
= 0
b. SFX
= 0, SFY
= 0, St
= 0
c. St
= 0
d. SFY
= 0
e. SFx
= 0, SFY
= 0
65. What
condition or conditions are necessary for static equilibrium?
a. SFx
= 0
b. SFX
= 0, SFY
= 0, St
= 0
c. St
= 0
d. SFY
= 0
e. SFx
= 0, SFY
= 0
66. A
heavy boy and a lightweight girl are balanced on a massless seesaw.
If they both move forward so that they are one-half their original
distance from the pivot point, what will happen to the seesaw?
a. The side the boy is sitting on
will tilt downward.
b. The side the girl is sitting on
will tilt downward.
c. Nothing, the seesaw will still be
balanced.
d. It is impossible to say without
knowing the masses and the distances.
67. The
condition for rolling without slipping is that:
a. VCM
= 2 rw
b. VCM
= rw2
c. VCM
= rw/2
d. VCM
= rw
68. Consider
a rigid body that is rotating. Which
of the following is an accurate statement?
a. Its center of rotation is its
center of gravity.
b. All points on the body are moving
with the same angular velocity.
c. All points on the body are moving
with the same linear velocity.
d. Its center of rotation is at
rest, i.e., not moving.
69. Consider a car with its wheels rolling (not sliding) on the road. How fast must the auto move for some point on a wheel to reach the speed of sound? (hint: Look at fig 8.1 on p. 252)
a. 2 times as fast
b. 1/2 times as fast
c. 20.5 times as fast
d. equal to the speed of sound