# Q2S - angular speed ω while the string makes angle θ with...

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Quiz 2 Solutions Check the best answer. 1. A woman stands on an ordinary bathroom scale located in an elevator. Which of the following situations will result in the highest reading on the scale? The elevator accelerates downward. [Less than at rest.] The elevator moves upward with constant velocity. [Same as at rest.] The elevator accelerates upward. [More than at rest.] The cable breaks and the elevator is in free fall. [Zero.] Check T or F depending on whether the statement is true or false. 2. The reason that highway curves are banked is to use the normal force exerted by the road to help provide the radial acceleration. T F Physics 53 Summer 2010 1

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3. A small sphere of mass m is attached to a massless string of length , which is attached to a ceiling. The sphere swings around in a horizontal circle at constant
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Unformatted text preview: angular speed ω , while the string makes angle θ with the vertical. Give answers in terms of m , g , and . a. Draw the free body diagram for the sphere. b. What is the string’s tension? [What is the radius of the circle, in terms of and ?] c. What is the angle ? a. Drawing below. b. The radius of the circle is sin , so the radial acceleration is a r = sin ⋅ 2 . The radial force is T sin , so we have T sin = ma r = m sin ⋅ 2 , or T = m 2 . c. Since the vertical forces add to zero we have T cos = mg . Using (b) we Fnd cos = g / 2 . [Note that this requires 2 ≥ g / .] Physics 53 Summer 2010 2 m g T...
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## This note was uploaded on 10/19/2011 for the course PHYSICS 53L taught by Professor Mueller during the Spring '07 term at Duke.

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Q2S - angular speed ω while the string makes angle θ with...

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