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Practice-Quiz7

# Practice-Quiz7 - Answer the torque points out of the page...

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Physics 7B Practice Quiz 7 First two letters of last name: DL Section Number ____________ Name (last, first) ____________________________ Student ID _______________________ I certify by my signature that I will abide by the code of academic conduct of the University of California. Signature No books or notes. Calculators OK. Show all your work below. Answers alone do not receive credit! 1. You are standing at the edge of a diving board which extends 2 m beyond its center support (marked A in the figure). a) (1.5 pts) If your mass is 70 kg, what is the magnitude of the torque at point A, neglecting the mass of the diving board? Answer: the torque is (70 kg)(10 m/s 2 )(2 m) = 1400 N-m b) (1.5 pts) What is the direction of the torque vector around point A?
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Unformatted text preview: Answer: the torque points out of the page at point A. 2. (1.5 pts) A playground carousel of radius 2 m is rotating with an angular velocity of 1 rad/s. You run and jump onto the edge of the carousel by matching your speed to that of the edge of the carousel. After you have jumped on, does the angular velocity of the carousel change? Discuss this in a few sentences using the concepts of angular momentum and rotational inertia. Answer: After jumping on, the carousel+you continue rotating at the same angular velocity as the carousel alone did. Angular momentum is conserved in this process: there are no external torques applied to the closed system (you + carousel). L = I ω τ = l F ⊥ K rot = ½ I ω 2...
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