Question

a particle of mass 4m explode in air in four equal masses with velocity v making angle 90 degree to each other then find its kinetic energy.

Answer 1

Since equal masses are exploding in 90 degrees with each other so the momentum will be zero here.

let's calculate kinetic energy for each

KE =$\frac12mv^2$

similarly we have three more masses of mass m

total KE = $4\times\frac12\times mv^2=2mv^2$