physics 121 exam 2 solutions

physics 121 exam 2 solutions - Name _ last first Student ID...

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Name ___________________________________ Student ID Number ____________ last first Physics 121A, Summer 2010 Exam 2, page 1 I. A ball with two strings attached follows the dotted circular path, a horizontal circle of diameter 0 . 74 m. The ball has mass m = 0 . 91 kg, and each string makes a different angle to the vertical as shown. Assume that the motion is uniform circular motion, and ignore air resistance. 1. (4 pts) Which choice best represents unlabeled free body and “ma” diagrams of the ball at the instant shown in the side view above ? Assume a fixed reference point, not moving with the ball. A B C D E 2. (5 pts) Suppose that the tension in the upper string is known to be 36 N. Which choice best represents the magnitude of the tension in the lower string? 38 N 36 N 32 N 15 N zero N A B C D E 50º 35º = = = = =
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Name ___________________________________ Student ID ____________ Score_______ last first Physics 121A, Summer 2010 Exam 2, page 2 I. Conical Pendulum, continued The figure is repeated for convenience. Recall that the circle diameter is 0 . 74 m, and the mass of the ball is 0 . 91 kg. 3. (5 pts) Which choice best represents the speed of the ball assuming that the upper string tension is still 36 N? 3 . 4 m/s 4 . 3 m/s 18 m/s 3 . 6 m/s 13 m/s A B C D E The angular speed ω of the ball is now very slowly increased as time goes by. Suppose that either string will break if its tension equals or exceeds 42 N. 4. (4 pts) Which string will break first if they both have the same strength? A. The upper string. B. The lower string. C. Both will break simultaneously when the speed gets too large. D. Need more information.
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This note was uploaded on 10/07/2010 for the course PHYS 121 taught by Professor Pedigo during the Spring '09 term at University of Washington.

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physics 121 exam 2 solutions - Name _ last first Student ID...

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