A sphere of mass `8m` collides elastically (in one dimension) with a block of mass `2m`. If the initial energy of sphere is E. What is the final energy of sphere?

Options

A. 0.8 E
B. 0.36 E
C. 0.08 E
D. 0.64E

Answer

B

Explanation

For elastic collision in one dimension
`v_(1)=(2m_(2)u_(2))/(m_(1)+m_(2))+(m_(1)-m_(2)u_(1))/(m_(1)+m_(2))`
As mass 2m,is at rest,So `u_(2)=0`
`impliesv_(1)=((8m-2m)u)/(8m+2m)=(3)/(5)u`
Final energy of sphere =`(K.E.)_(f)`
`(1)/(2)(8m)((3u)/(5))^(2)=(1)/(2)(8m)u^(2)xx((3)/(5))^(2)=(9)/(25)E`.
0.36E