Physics Help Forum Energy, work and power question

 Energy and Work Energy and Work Physics Help Forum

 Apr 28th 2017, 04:10 AM #1 Junior Member   Join Date: Mar 2017 Posts: 5 Energy, work and power question I can't work out why I'm getting the part ii wrong and I was wondering if you could help. A mouse of mass 15g is stationary 2m below its hole. It runs to its hole, arriving 1.5 seconds later with a speed of 3ms^-1. i) Show that the acceleration of the mouse it not constant. [Done by using s=ut+.5at^2 and v=u+at and showing that they give different answers for acceleration] ii) Calculate the average power of the mouse Since power = work done / time and work done = .5mv^2 - .5mu^2, power = ((0.5*0.015*3^2) - 0) / 1.5 =0.045W. However, the book gives the answer 0.241W.
 Apr 28th 2017, 04:51 AM #2 Physics Team     Join Date: Jun 2010 Location: Naperville, IL USA Posts: 2,233 Don't forget that the work done includes both the gain in KE and the gain in PE as the mouse runs up hill.
 Apr 28th 2017, 05:05 AM #3 Junior Member   Join Date: Mar 2017 Posts: 5 Oh, of course! power = ((0.5*0.015*3^2) + 0.015g*2) / 1.5 = 0.241W Thanks ChipB

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