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Unformatted text preview: 1.0 m/s (C) 0.67 m/s    2 3 (s)  1 0 4 I2 – (E) 1.3 m/s 4 – (c) [4pt] A mass swinging from a rope is at the
position shown. At this instant, which arrow
correctly shows the direction of the net torque
on the mass about a pivot where the rope
attaches to the ceiling? Arrow (A) is out of the
page, and (D) is into the page.
(A) (B)
The (C) (D) righthand (E)
rule (F) shows Pivot
(A) ʘ (B) (F) that (C)
(E) (D) is into the page. The
tension in the rope doesn’t contribute
to the net torque because it is antiparallel to and has no lever arm. (d) [4pt] An 840 g cylinder has an apparent mass of 680 g when submerged in water. What is
its density?
(A) 1.24 g/cm3 (B) 4.25 g/cm3 (C) 5.25 g/cm3 (D) 8.90 g/cm3 The buoyant force is the weight of 160 g of water, which has a volume of 1 g/cm 3.
Therefore, the volume of the cylinder is 160 cm3, and the metal has a density of 5.25
g/cm3. 7 (e) [4pt] A 300 kg turntable, which is a uniform cylinder with moment of inertia
where is the radius, rotates at 6 RPM. Four people, each with a mass of 75 kg, step radially
inward onto the edge. What is the rotational rate after they step on?
(A) 1 RPM (B) 2 RPM Each person contributes (C) (D) 3 RPM to the moment of inertia, with 4 RPM
kg, so the total moment of inertia with the people is
since Therefore, implies that RPM. (f) [4pt] A 2.5kg mass is acted on by a timedependent net for...
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 Fall '12
 ScottYost
 Physics

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