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Part A
1a. A (True)
1b. A (True)
1c. A (True)
1d. B (False)
2. E
3. A (the closer that the overall mass distribution is
located to the spin axis, the smaller the moment of inertia of
the object)
4. F
5. B and D (if moment of inertia is constant, then in order
for L to be decreasing, angular speed must also be decreasing)
6a. C
6b. F (if R of a sphere doubles, its mass increases
by 8x, so its entire moment of inertia increases by 32x)
7a. B
7b. E
7c. F
7d. G
8. B (want largest possible lever arm, and force as perpendicular
as possible to lever arm direction)
Part B
1a. 8.6 m/s (conservation of energy: KE of pair of cars
is converted to work done by friction force)
1b. 15 m/s = 34 mi/h (using conservation of momentum through
the collision)
2. 0.76 away from the fulcrum, on Bryce's side (find position of Crystal so that total center-of-mass lies exactly at fulcrum position; OR sum torques of all three children about fulcrum/pivot and set equal to zero)
3. F_spring = 2.8 x 10^3 N