A ball is thrown vertically down from a height of 40m from the ground with an initial velocity .v.. The ball hits the ground, loses one-third of its total mechanical energy and rebounds back to the same height. If the acceleration due to gravity is 10ms^(-2), the value of .v. is

A ball is thrown vertically down from a height of 40m from the ground

1.	A ball is thrown vertically down from a height of 40m from the ground with an initial velocity .v.. The ball hits the ground, loses one-third of its total mechanical energy and rebounds back to the same height. If the acceleration due to gravity is 10ms^(-2), the value of .v. is
Answer» `5 ms^(-1)` `10 ms^(-1)` `15 ms^(-1)` `20 ms^(-1)` ANSWER :D