Question

A piece of ice falls from a height `h` so that it melts completely. Only one-quarter of the heat produced is absobed 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 xx 10^(5) J//kg` and `g = 10 N//kg`]
A. 544 km
B. 136km
C. 68 km
D. 34km

Answer 1

Correct Answer - B
b) According to quesion as conservation of energy, energy grained by the ice during its fall from height h is given by
E =mgh
So, `(mgh)/4 = mL_(f)`
As given, only one quarter of its energy is absorbed by the ice.
So, `(mgh)/4 = mL_(f)`
`rArr h=(mL_(f) xx 4)/(mg) = (L_(f) xx 4)/g = (3.4 xx 10^(5)xx4)/10 = 13.6 xx 10^(4)`
=13600 m = 136 km