Can any object have mechanical energy even if its momentum is zero? Explain.

The power of a motor pump is $2 \mathrm{kW}$. How much water (in kilogram) per minute the pump can raise to a height of $10 \mathrm{m}?$

(Given $g=10 \mathrm{m} {\mathrm{s}}^{-2}$, only write the magnitude of the answer in the given box, no need to write the unit.)

The weight of a person on a planet $A$ is about half that on the earth. He can jump up to $0.4 \mathrm{m}$  height on the surface of the earth. How high he can jump on the planet $A?$