Question

Consider the situation as shown in the diagram , the ball strikes the wall normally and the collision is elastic , the change in the kinetic energy of the ball is

A. `30 J`
B. `60 J`
C. `90 J`
D. `120 J`

Answer 1

Correct Answer - B
Before collision
After collision
`v_(1) - v_(2) = -e( u_(1) - u_(2))` , here `e = 1`
`v_(1) - 20 = -1( -10 - 20) rArr v_(1) = 50 m//s`
For ball , `Delta K = (1)/(2) m (v_(1)^(2) - u_(1)^(2))`
For ball , `Delta K = (1)/(2) m(v_(1)^(2) - u_(1)^(2))`
`= (1)/(2) xx 50 xx 10^(-3) (50^(2) - 10^(2)) = 60 J`