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exam3sol - Version 078 exam3 markert(58840 This print-out...

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Version 078 – exam3 – markert – (58840) 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Suppose that a volleyball A and a bowling ball B are completely submerged in water and have the same volume, as in the figure. (Of course, you would have to hold the volleyball beneath the water to keep it from popping up to the surface.) A B Which feels a greater buoyant force? 1. volleyball A 2. bowling ball B 3. They feel the same buoyant force. cor- rect 4. Unable to determine Explanation: They feel the same buoyant force because they displace the same amount of water. 002 10.0 points Water with air bubbles flows through a pipe that gets narrower. In the narrow region the water gains speed and the bubbles are 1. same size. 2. larger. cor- rect 3. smaller. Explanation: As water gains speed, pressure in the water decreases according to Bernouli’s principle. Decreased water pressure squeezes less on air bubbles, allowing them to expand — so that air pressure and surrounding water pressure match. If the moving water continues its flow into a wider section of pipe, speed decreases, pressure increases, and the bubbles become smaller. 003 10.0 points A bowling ball is both sliding and spinning on a horizontal surface such that its rotational kinetic energy equals its translational kinetic energy. What is the ratio of the ball’s center-of- mass speed to the tangential speed of a point on its surface? 1. 0 . 33 2. 1 3. 0 . 73 4. 0 . 5 5. 0 . 63 correct Explanation: v t = R ω and the inertia is I = 2 5 m R 2 , so K trans = K rot 1 2 m v 2 = 1 2 I ω 2

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Version 078 – exam3 – markert – (58840) 2 = 1 2 parenleftbigg 2 m R 2 5 parenrightbigg parenleftBig v t R parenrightBig 2 = 1 5 m v 2 t v 2 v 2 t = 2 5 v v t = radicalbigg 2 5 = 0 . 632456 . keywords: 004 10.0 points A rod of negligible mass is pivoted at a point that is off-center, so that length 1 is different from length 2 . The figures show two cases in which masses are suspended from the ends of the rod. In each case the unknown mass m is balanced by a known mass 65 kg or 59 kg so that the rod remains horizontal.
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exam3sol - Version 078 exam3 markert(58840 This print-out...

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