qz6sol_7193f10 - . When the boy loses contact with the ice,...

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TA: Tomoyuki Nakayama Monday, October 11, 2010 PHY 2048: Physic 1, Discussion Section7193 Quiz 6 (Homework Set #7) Name: UFID: Formula sheets are not allowed. Calculators are allowed. Do not store equations in your calculator. You need to show all of your work for full credit. ________________________________________________________________________________ A boy is initially at the top of a hemispherical ice mound of radius R = 15.0 m. He begins to slide down the ice, with an initial speed of 10.0 m/s. a) When the boy loses contact with the ice, what is the speed of the boy? Let the angle of the boy’s position from the vertical be
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Unformatted text preview: . When the boy loses contact with the ice, the normal force becomes zero. However, the boy is still in a circular motion. Newtons 2 nd law yields m(v 2 /R) = mgcos The normal force does not do work on the boy. Therefore, the mechanical energy of the boy is conserved. (1/2)mv 2 + mgR = (1/2)mv 2 + mgRcos Solving the equations simultaneously for v, we get v = (v 2 /3 + 2gR/3) = 11.5 m/s b) At what height does the boy lose contact with the ice? From the first equation in part a), the angle is cos = v 2 /Rg = 0.900 The boy loses contact at height h = Rcos = 13.5 m...
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