Question

At $30^{\circ }C$, a lead bullet of $50g$, is fired vertically upwards with a speed of $840m/s$. The specific heat of lead is $0.02cal/g^{\circ }C$. on returning to the starting level, it strikes to a cake of ice at $0^{\circ }C$. Calculate the amount of ice melted (Assume all the energy is spent in melting only)

• A. $62.7g$
• B. $55kg$
• C. $52.875kg$
• D. $52.875g$

Answer 1

The correct option is D $52.875g$

Kinetic energy of bullet = $\frac{m{v}^2}{2}$=$\frac{1}{2}\times 0.02\times {840}^2$ = $17640joule=4200cal$

heat supplied by lead to ice : $\Delta H_1=ms\Delta T$ = $50\times 0.02\times 30$ = $30cal$

Total heat supplied = $4200+30=4230cal$

let $M_i$ mass of ice melted $L$ is the latent heat of ice

$M_{i}L=4230$

$M_i\times 80=4230$

$M_i=52.875g$