Saturday, 9 June 2018

classical mechanics - Thermal energy generated due to loss in kinetic energy when observed from two different frames of reference


A body is moving with a velocity v with respect to a frame of reference S1.


It bumps into a very heavy object and comes to rest instantaneously, its kinetic energy


12mv2


as seen from the frame S1 is completely converted to thermal energy.


Now, a man moving with a uniform velocity V (in the direction of the body) with respect to S1 observes the body. He notes that its initial kinetic energy of the body is



12m(v+V)2,


and that after it rams into the heavy body as


12mV2,


and concludes that the thermal energy produced is the difference


12m(v+V)212mV2 = 12mv2+mvV.


Which of the two answers is correct and why?




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