Question

Does the transfer of energy take place when you push a huge rock with all your might and fail to move it? Where is the energy you spend going?

Answer 1

Hint:Think whether the rock moves or not. Remember that for transfer of energy from one body to another body, work needs to be done on an object or by an object.No work is done if either force or displacement is zero.

Complete answer:
When we push a huge rock with all our might, still the rock doesn’t move. This is because the frictional force experienced by the rock is still greater than the force we apply. Hence the displacement is zero.

Work done is the scalar product of force and displacement. Displacement being zero, the work done is also equal to zero. Thus no work is done by the man and no work is done on the rock.

Hence there is no transfer of energy. The muscular energy of ours doesn’t get converted to kinetic energy. Instead due to friction, it gets converted to heat energy. Hence we lose out energy.This is the reason we feel exhausted even though there is no work done.

Note: Students should know that for transfer of energy, work must be done. And with zero displacement the work done is also zero. Also energy can never be created nor be destroyed. Thus the energy spent by us must be released in any form. For this the friction plays a role and converts into heat energy.