Does work done depend upon the velocity of the body?

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

$A$ man weighing $70 \,kg$ carries a weight of $10 \,kg$ to the top of a tower $100 \,m$ high. Calculate the work done.

When a coil spring is compressed,the work is done on the spring. The elastic potential energy:

Find the velocity of a body of mass $100 \, g$ having a kinetic energy of $20 \, J$. (in $, m s^{-1}$)

An automobile engine propels a $1000 \,kg$ car $(A)$ along a levelled road at a speed of $36 \,km \,h^{-1}$. Find the power if the opposing frictional force is $100 \,N$. Now,suppose after travelling a distance of $200 \,m$,this car collides with another stationary car $(B)$ of the same mass and comes to rest. Let its engine also stop at the same time. Now car $(B)$ starts moving on the same level road without its engine started. Find the speed of the car $(B)$ just after the collision.