Question

A boy of mass m and a girl of mass 2m are initially at rest at the center of a frozen pond. They push each other so that she slides to the left at speed v across the frictionless ice surface and he slides to the right. What is the total work done by the children?

Answer 1

Answer:

Explanation:

Given

mass of boy is m

mass of girl is 2 m

Speed of girl is v towards left

Let u be the speed of boy after push

Conserving momentum

0=2m(v)+mu

u=-2v

Kinetic Energy of girl after push$=\frac{2mv^2}{2}=mv^2$

Kinetic Energy of boy after Push$=\frac{m(2v)^2}{2}=2mv^2$

Total Kinetic Energy $=3mv^2$

Thus Work done =total Kinetic Energy$=3mv^2$