Question

A block of ice with mass $m$ falls into a lake. After impact, a mass of ice $\frac{m}{5}$ melts. Both the block of ice and the lake have a temperature of $0^{\circ }C$. If $L$ represents the heat of fusion, the minimum distance the ice fell before striking the surface is

• A. $\frac{L}{5g}$
• B. $\frac{5L}{g}$
• C. $\frac{gL}{5m}$
• D. $\frac{mL}{5g}$

Answer 1

The correct option is A $\frac{L}{5g}$

Using Energy conservation,
the energy loss due to potential energy goes into melting of ice
$\frac{m}{5}\left(L\right)=mgh$
$\Rightarrow h=\frac{L}{5g}$