Name _________________
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g = 9.80m/s
2
Problem 1
(2 points each)
A crazed physicist risks his life rotating on a frictionless stool.
When he pulls his arms in he spins faster.
Give
the signs of the changes in kinetic energy, angular momentum and angular velocity.
Answer +,  or 0.
______ [i]
Δ
K
______ [ii]
Δ
L
______ [iii]
Δ
ω
Problem 2
A 3kg mass is at (3m,4m), a 5kg mass is at (0,4m) and a 2kg mass is at (2m,0). (6 points each)
(a) What are the coordinates of the center of mass?
(b) What is the moment of inertia for rotations about the
y
axis?
Problem 3
(a) A 200 g glider moves at 0.3 m/s on an air track toward a 300 g glider moving in the opposite direction at
0.1 m/s.
If the collision is elastic then what are both final velocities? (8 points)
(b) Before being hit by a bat, a 0.15kg baseball has a velocity of
−
40,0
m/s
.
It leaves the bat with velocity
45,25
m/s
.
If the bat is in contact with the ball for 0.05s then what is the average force of the bat on the ball?
(7 points)
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 Spring '09
 Angular Momentum, Friction, Kinetic Energy, Mass, Angular velocity

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