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Homework Help: Energy conversion with constant velocity

  1. Apr 16, 2013 #1
    This is just a very simple conceptual question.

    Say that someone is going down an escalator at a constant velocity. They are losing GPE, but not gaining any KE. So where is this potential energy going? Same with going up, they're gaining GPE, but not losing any KE.

    On a similar note, say that a crane is lifting a box upwards with a constant force, but now the box is accelerating upwards. The box is gaining GPE as well as gaining KE. Where is this energy coming from? What is losing energy accordingly?

  2. jcsd
  3. Apr 16, 2013 #2


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    2017 Award

    Staff: Mentor

    It is lost in heat, or can be used to compress a spring, or convert it to other forms of energy.
    In the same way, to go up, you have to use chemical energy stored in your body (and you have to eat to refill this).
    The fuel, in the crane or in a power plant*. Cranes need a lot of power.

    *or the sun, the wind, or whatever is used to produce electric power
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