0 5 10 15 20 25 30 0 2 4 6 Time (s) X (m) 8

P211 Final Sample 1
21) A flying saucer deep in interstellar space, free of external forces, rotates about its symmetry axis
with angular velocity ω. The aliens inside the saucer rearrange the furniture to make room for a
Christmas tree they have just procured from Elvis. As a result the angular velocity of the saucer
increases to 2ω. If originally the rotational kinetic energy of the saucer was K, after the
rearrangement its new rotational kinetic energy is:
A) K/4 B) K/2 C) K
D) 2K E) 4K
22) A block of mass M = 4 kg is resting on a frictionless table and is attached to an uncompressed,
unstretched spring (k = 460 N/m) fixed to a wall at the other end, as in the figure below. A bullet of
mass m = 0.06 kg is fired into the block in a direction parallel to the alignment of the spring, with a
speed of v b = 100 m/s, and is embedded in the block. What is the amplitude x m of the resulting
simple harmonic motion? (Hint: energy is not conserved during the collision between the bullet and
the block, but momentum is; during oscillations, energy is conserved, but not momentum.)
x = 0 x = 0
−x m
+x m
M
v b
m
M+m
Initially
Finally
A) 0.052 m B) 0.139 m C) 0.211 m
D) 0.876 m E) 1.74 m
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