Question

From which height a block of ice must be dropped in order that it melts completely. Assume that all the energy is retained by the ice .
($g=10m{s}^{-2}$, $L=80Jg{m}^{-1}$and J $=$ 4.2 J/cal)

• A. 1000Km
• B. 100Km
• C. 33.6Km
• D. 1Km

Answer 1

Answer: (C)

33.6Km

The entire potential energy of the waterfall will be converted into heat energy.
$mgH=JmL$
$10\times H=80\ast 4.2\ast {10}^3$
$\Rightarrow H=33.6Km$