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Homework Help: Heat Engine lifting a mass

  1. May 9, 2010 #1
    1. The problem statement, all variables and given/known data
    A heat engine operating between temperatures of 500 K and 300 K is used to lift a 10-kilogram mass vertically at a constant speed of 4 meters per second.

    (a) Determine the power that the engine must supply to lift the mass.

    (b) Determine the maximum possible efficiency at which the engine can operate.

    (c) If the engine were to operate at maximum possible efficiency, determine the following:

    i. The rate at which the hot reservoir supplies heat to the engine
    ii. The rate at which heat is exhausted to the cold reservoir

    2. Relevant equations
    F = ma
    W = FD
    Pavg = Change in Work / Change in Time

    3. The attempt at a solution

    (a) F = ma
    F = 10 kg * 9.8 m/s^2
    F = 98 N

    How can I find power without being given a displacement? Power is a function of work and time, and work is a function of force and displacement - All I have is force.

    Solution attempts for B and C forthcoming when I figure out A.
  2. jcsd
  3. May 9, 2010 #2


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    Homework Helper

    Output power also defined as W = F*v, where v is the velocity.
    Temperatures of the source and sink is given.Find the efficiency of the engine.
    Efficiency = Output power/Input power.
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