A man standing on the edge of a roof of a 20 m tall building projects a ball of mass 100 g vertically up with a speed of 10 ms^(-1) and simultaneously throws another ball of same mass vertically down with the same speed. Find the kinetic energy of each ball when they reach the ground. (g=10 ms^(-2))

A man standing on the edge of a roof of a 20 m tall building projects

1.	A man standing on the edge of a roof of a 20 m tall building projects a ball of mass 100 g vertically up with a speed of 10 ms^(-1) and simultaneously throws another ball of same mass vertically down with the same speed. Find the kinetic energy of each ball when they reach the ground. (g=10 ms^(-2))
Answer» Solution :Both the two BALLS reach the ground with the same VELOCITY `h=20m, m=100 g=10^(-1)KG, U=10 ms^(-1)` `V^(2)-u^(2)=2gh` `v^(2)=u^(2)+2gh=10^(2)+2xx10xx20-500` K.E. of each ball `= (1)/(2)mv^(2)=(1)/(2)xx10^(-1)xx500=25 J` `therefore` K.E. of ball = 25 J.