Question

A gun fires a lead bullet of temperature 300K into a wooden block. The bullet having melting temperature of 600 K penetrates into the block and melts down. If the total heat required for the process is 625 J, then the mass of the bullet is ___ grams.

(Latent heat of fusion of lead \( =2.5 \times 10^{4}\ \mathrm{JKg}^{-1}\) and specific heat capacity of lead \(=125 \ \mathrm{JKg}^{-1} \mathrm{~K}^{-1}\))

(1) 20

(2) 15

(3) 10

(4) 5

Answer 1

Correct option is : (3) 10

\(625=\mathrm{ms} \Delta \mathrm{T}+\mathrm{mL}\)

\( 625=\mathrm{m}\left[125 \times 300+2.5 \times 10^{4}\right]\)

\( 625=\mathrm{m}[37500+25000]\)

\( 625=\mathrm{m}[62500]\)

\( \mathrm{m}=\frac{1}{100} \mathrm{kg}\) 

M = 10 grams