Question

Consider a long metal rod lying on the floor. One end of the rod is fixed to the wall. You add heat Q to the rod with a blow torch. During this process, due to thermal expansion, the rod increases in length from 1 m to 1.05 m. As it expands, the rod does some work, pushing a mass along the floor exerting a constant force of 1000 N on the block. The total thermal energy of the rod increases by 200 J during this process. Assume that the only energy exchange between the rod and its environment is the heat you add and the work done by the rod.

How much heat did you add (what is Q)? Express your answer in units of Joules, but enter only the numeric answer.

Answer 1

Total heat energy added= Work done in expanding the rod + work done in moving the block

given the work done in expanding i.e the change in thermal energy of rod = 200 J

now we need to find the work done in moving the mass W=

here the force is constant and is parallel to the diatnce moved by the rod so

Force = 1000N d= 0.05 m

W=1000 X0.05 = 50 J

Q= 200 +50 = 250 J

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