A body of mass 5 kg collides elastically with a stationary body of mass 2.5 kg. After the collision, the 2.5 kg body begins to move with a kinetic energy of 8). Assuming the collision to be one-dimensional, the kinetic energy of the 5 kg body before collision is:

Options

A. 3 J
B. 6 J
C. 9 J
D. 11J

Answer

c

Explanation

Here we know that the fraction of K.E. transferred
=`(4x)/((1+x)^2)=(4xx1/2)/((1+1//2)^2)`
=8/9
This means that
`("K.E of 2.5 Kg after collison")/("K.E of 2.5 Kg before collison")=8//9`
`:.` K.E of 5 kg before collison is
`E_k=9//8xx8=9 J`