Observing Energy in Free Fall

Q. A body moves in a vertical circle of radius r from the lowest point to highest point. What is the amount of work done by gravity? (Assume mass of the body to be 'm' kg and acceleration due to gravity to be $gm{s}^{-2}$)

1. 2mgr
2. -2mgr
3. mgr
4. mgr

Q.

A ball is dropped from a height h. The velocity of the ball when it reaches the ground is $10m{s}^{-1}$. Find h.(Take $g=10m{s}^{-2}$).

Q. An object dropped from a height of $20m$ is undergoing free fall. What is its velocity just before it touches the ground? (Take $g=10m{s}^{-2}$)

1. $10m{s}^{-1}$
2. $20m{s}^{-1}$
3. $17m{s}^{-1}$
4. $15m{s}^{-1}$