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154-wk-08

154-wk-08 - HPHY 154 Workout 08 Work Prof A E Bak Name Work...

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HPHY 154 Workout 08 Work Prof. A. E. Bak Name Work is the effect of force acting over displacement. For a force f acting over a path C of displacement, the work W done is defined by W ! " C f ! dl , where dl is an infinitesimal displacement along C . For a constant force acting over a displacement D , this definition yields simply W ! f ! D ! fD cos ! , where ! is the tail-to-tail angle between f and D . 1. S&J Problem 7-2 (formerly S&B Problem 7-2). A shopper in a supermarket pushes a cart with a 35.0-N force directed at an angle of 25.0 # below the horizontal. Find the work done by the shopper as he moves down an aisle 50.0 m long. 2. In order to push a 25.0- kg crate up a frictionless incline, angled at 25.0 # to the horizontal, you exert a 209-N force parallel to the incline. As the crate slides 1.50 m , what work is done on the crate by: a. you. b. the gravitational force. c. the normal force exerted by the incline. 3. S&J Problem 7-20 (formerly S&B Problem 7-25). As shown in Figure P 7.20 (on page 211), a small mass m is pulled to the top of a frictionless half-cylinder of radius R by a cord that passes over the top of the half-cylinder. a. If the mass moves at constant speed, then show that f ! mg cos ! . Hint: The tangential acceleration a s is zero here.

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154-wk-08 - HPHY 154 Workout 08 Work Prof A E Bak Name Work...

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