A piece of ice falls from a height h so that it melts completely. Only one — quarter of the heat produced is absorbed by the ice and all energy of ice gets converted into heat during its fall. The value of h is
[Latent heat of ice is 3.4 × 105 J/kg and g = 10 N/kg]
(A) 136 km
(B) 68 km
(C) 34 km
(D) 544 km
(A) 136 km
When the piece of ice falls from the height h, it possesses potential energy, mgh.
This P.E. is converted to heat energy.
∴ Q = mgh
But only \(\frac{1^{th}}{4}\) of it is absorbed by ice which is used to change the state.
∴ \(\frac{mgh}{4}\) = mL
∴ \(\frac{10\times h}{4}\) = 3.4 × 105
∴ h = 13.6 × 104 m = 136 km