Question

A thin hollow sphere of mass m is completely filled with
water of mass m. Now it is kept in a refrigerator and
cooled to below 0°C. It is taken out and made to roll
without slipping on a horizontal surface with a velocity u.
The kinetic energy of the system is (Assume no heat is
gained by the sphere)​

Answer 1

mass of hollow sphere is m

mass of filled water is also m

total mass becomes 2m

even after cooling mass of water remain same..so total mass remains 2m

k.e = 1/2mv²

k.e=1/2×2m.u²=mu²