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NAME:
FORM A
PHYSICAL PRINCIPLES 1
EXAM 3
1. Two marbles, one twice as heavy as the other, are dropped to the ground from the roof
of a building. Just before hitting the ground, the heavier marble has
A. as much kinetic energy as the lighter one.
B. twice as much kinetic energy as the lighter one.
C. half as much kinetic energy as the lighter one.
D. four times as much kinetic energy as the lighter one.
E. impossible to determine
2. A block initially at rest is allowed to slide down a frictionless ramp and attains a speed v at the
bottom. To achieve a speed 2v at the bottom, how many times as high must a new ramp be?
A. 1
B. 2
C. 3
D. 4
E. 5
3. A spring-loaded toy dart gun is used to shoot a dart straight up in the air, and the dart reaches a
maximum height of 24 m. The same dart is shot straight up a second time from the same gun, but
this time the spring is compressed only half as far before firing. How far up does the dart go this
time, neglecting friction and assuming an ideal spring?
A. 96 m
B. 48 m
C. 24 m
D. 12 m
E. 6 m
4. Suppose rain falls vertically into an open cart rolling along a straight horizontal track with
negligible friction. As a result of the accumulating water, which happens?
A. speed decreases, momentum unchanged, and kinetic energy decreases
B. speed decreases, momentum unchanged, and kinetic energy increases
C. speed unchanged, momentum unchanged, and kinetic energy unchanged
D. speed unchanged, momentum decreases, and kinetic energy decreases
E. None of these
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5. You are suppose to find the muzzle speed of bullets fired from a new advanced military rifle.
First, you find the mass of each bullet to be 100 grams. Next, you fire the weapon straight up into
a 9.9 kg block of wood, into which it imbeds itself. The wood is blasted straight up into the air to
an amazing height of 5 m. What speed did you find? (NOTE:1 gr. = 0.001 kg)
A. 989.9 m/s
B.1204 m/s
C. 27,000 m/s
D.4000 m/s
E. None of these
6. Suppose you are on a cart, initially at rest on a track with very little friction. You throw balls at
a partition that is rigidly mounted on the cart. If the balls bounce straight back as shown in the
figure, is the cart put in motion?
A. Yes, it moves to the right.
B. Yes, it moves to the left.
C. No, it remains in place.
D. Need more information
E. None of these
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7. A ladybug sits at the outer edge of a merry-go-round, and a gentleman bug sits halfway
between her and the axis of rotation. The merry-go-round makes a complete revolution once each
second.The gentleman bug’s angular speed is:
A. half the ladybug’s.
B. the same as the ladybug’s.
C. twice the ladybug’s.
D. impossible to determine
E. none of these
8. A disk and a hoop of the same mass and radius are released at the same time at the top of an
inclined plane. Does the disk reach the bottom of the plane
A. before the hoop
B. after the hoop
C. same time as the hoop
D. need more information
E. none of these
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9. Four identical particles, each with mass m, are arranged in the x, y plane as shown. They are
connected by light sticks to form a rigid body. If m = 2.0 kg and a = 1.0m, the rotational
inertia of this array about the y axis is:
A. 4.0 kg · m2
B. 12 kg · m2
C. 9.6 kg · m2
D. 4.8 kg · m2
E. none of these
10. A flywheel is initially rotating at 20 rad/s and has a constant angular acceleration. After 9.0 s
it has rotated through 450 rad. Its angular acceleration is:
A. 3.3 rad/s
B. 4.4 rad/s
C. 5.6 rad/s
D. 6.7 rad/s
E. 11 rad/s
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SHOW ALL YOUR WORK!
NAME
(7.5 POINTS)
A 1.5 kg block is at rest on a ramp of height h. When the block is released, it slides
without friction to the bottom of the ramp, and then continues across a surface that is
frictionless except for a rough patch of width 10 cm that has a coefficient of kinetic
friction k = 0.640. Find h such that the block’s speed after crossing the rough patch is
3.5 m/s.
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SHOW ALL YOUR WORK!
NAME
(7.5 POINTS)
In a ballistic pendulum, an object of mass m is fired with an initial speed vi at the bob of a
pendulum. The bob has a mass M, and is suspended by a rod of neglible mass. After the
collision, the object and the bob stick together and swing through an arc, eventually
gaining a height h. Find the height h in terms of m, M, vi, and g.