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Unformatted text preview: 1.0 m/s (C) 0.67 m/s | | | 2 3 (s) | 1 0 4 I-2 – (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.
The (C) (D) right-hand (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
(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 2.5-kg mass is acted on by a time-dependent net for...
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- Fall '12