qz5sol_3891f10 - Newtons 2 nd law yields M(-g/4) = T Mg T =...

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TA: Tomoyuki Nakayama Tuesday, October 5, 2010 PHY 2048: Physic 1, Discussion Section 3891 Quiz 5 (Homework Set #6) 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 cord is used to vertically lower an initially stationary block of mass M = 8.00 kg at a constant downward acceleration of g /4. a) When the block has fallen a distance d = 2.50 m, what is the work done by the cord’s force on the block? We take our positive direction upward. Then the downward acceleration is expressed as –g/4.
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Unformatted text preview: Newtons 2 nd law yields M(-g/4) = T Mg T = 3Mg/4 = 58.8 N In our coordinate system, the displacement of the block is d. Thus the work done by the tension is W T = T(-d) = -147 J b) When the block has fallen the distance d = 2.50m, what is the kinetic energy of the block? The net force exerted on the block is F net = M(-g/4) = -19.6 N According to the work-energy theorem, the change in kinetic energy of the block is equal to the work done by the net force. Since the initial kinetic energy is zero, the kinetic energy of the block is K = W net = F net (-d) = +49 J...
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This note was uploaded on 01/25/2011 for the course PHY 2048 taught by Professor Field during the Summer '08 term at University of Florida.

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