A ball is dropped from height 20 m. If coefficient of restitution is 0.9, what will be the height attained after first bounce in m is?

If a body falls from height h, then from equation of motion we know that it will hit the ground with a velocity say u=  which is also the velocity of approach here. Now, if after collision it gains a height  then again by equation of motion , which is also the velocity of separation .so, by definition of e,

Given ,h=20 m, e=0.9

 height attained after first bounce