the amount of heat energy absorbed at contant temperature by unit mass of a solid to convert into liquid phase is called the specific latent heat of fusion
The specific latent heat of a substance is the amount of energy needed to change the state of 1 kg of the substance without changing its temperature. Each substance has two specific latent heats: latent heat of fusion (the amount of energy needed to freeze or melt the substance at its melting point)
sorry i dont know
moi of disc is (mr^2)/2 so for moi to be equal mass of disc should two times of mass of ring.