An object A of mass `1 kg` is projected vertically upward with a speed of `20 m//s`. At the same moment another object B of mass `3 kg`, which in intially above the object A, is dropped from a height `h = 20 m`. The two point like objects (A and B) collision and stick to each other. The kinetic energy is K (in J) of the combined mass after collision, find the value of `K//25`.

Answer

2

Explanation

Using relative motion, the time of collision `t = (h)/(20 + 0) = 1s`
By conservation of momentum for collision `3(10) + 1 (-10) = 4 (V) rArr V = 5 m//s`
`KE = (1)/(2) (4) (5)^(2) = 50J`