Question

A particle of mass 5 kg strikes a body of mass $2.5kg$ at rest elastically. The $2.5kg$ mass after collision moves with a kinetic energy of $5J$.The kinetic energy of 5 kg mass before collision is

• A. $0.62J$
• B. $5.625J$
• C. $7.68J$
• D. $4.20J$

Answer 1

The correct option is B $5.625J$

Applying Conservation of Momentum and equation of coefficient of restitution , we obtain the initial velocity of the 5kg mass to be approximately equal to 1.5m/s.
We finally get the answer to be 5.625J