State principles of conservation of energy

The principle of energy conservation states that energy is neither created nor destroyed. It may transform from one type to another

Explanation

... The common forms of energy include thermal, electrical, chemical, mechanical, kinetic, and potential. It may also be stated that the sum of all kinds of energy is constant.

since you're a real machine, your ama is always less than your ima, because you can never totally eliminate friction.

d

explanation:

v=uf/(u-f)

= 5.10/(5-10) convex lens has positive focal length

=50/-5

=-10 cm (formed at other side)