Is it practically possible to convert a form of energy completely into another useful form? Give reason.

In a shopping mall, while standing on an escalator you move from level 1 to 30 metre high level 4. What is the work done by you?

A man lifts a mass of 20 kg to a height of 2.5 m. Assuming that the force of gravity on 1 kg mass is 10 N, find the work done by the man.

A body when acted upon by a force of 10 kgf moves to a distance 0.5 m in the direction of force. Find the work done by the force. Take 1 kgf = 10 N.