From what height a piece of ice at zero degree fall in order that it may melt on reaching the ground, assuming no loss of energy on the way : (J = 4.2 J / cal)

Let m be mass of ice block and h be the height above the ground.∴Work done W = mgh.Heat produced  Q=WJ=mghJHeat required to melt ice block Q’ = mL∴mghJ=mLh=JLg=4.2×80×1039.8=3.4×104m=3.4×106cm