Work and Energy...

A pile driver drives postes into the ground by repeatedly dropping a heavy object on them. Assume the object is dropped from the same height each time. By what factor does the energy of the pile driver-Earth system change when the mass of the object being dropped is doubled?

A car weighing 600 kg traveling with $$72\, km/h$$ stops at a distance of $$60\ m$$ decelerating uniformly. What is the work done by brakes in joules?

1 kWh is equal to

A man carries a heavy box on his head on a horizontal plane from one place to another. In this case, he does

Energy cannot be measured in.

Sunil rolls a marble ball down a frictionless inclined plane as shown above. What kind of energies are possessed by the rolling marble ball?

Work done in time $$t$$ on a body of mass $$m$$ which is accelerated from rest to a speed $$v$$ in time as a function of time $$t$$ is given by

A man $${M}_{1}$$ of mass $$80kg$$ runs up a staircase in $$15s$$. Another man $${M}_{2}$$ also of mass $$80kg$$ runs up the stair case in $$20s$$. The ratio of the power developed by them will be:

A weight lifter lifts a weight off the ground and holds it up then:

An athlete in the Olympic games covers a distance of $$100$$m in $$10$$s. His kinetic energy can be estimated to be in the range. (Assume weight = 60kg)