1. Tardigrade
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  4. A lead bullet penetrates into a solid object and melts. Assuming that 40 % of its kinetic energy is used to heat it, the initial speed of bullet is: (Given, initial temperature of the bullet =127° C, Melting point of the bullet =327° C, Latent heat of fusion of lead =2.5 × 104 J Kg -1, Specific heat capacity of lead =125 J / kg K )

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Q. A lead bullet penetrates into a solid object and melts. Assuming that $40 \%$ of its kinetic energy is used to heat it, the initial speed of bullet is:
(Given, initial temperature of the bullet $=127^{\circ} C$,
Melting point of the bullet $=327^{\circ} C$,
Latent heat of fusion of lead $=2.5 \times 10^{4}\, J \,Kg ^{-1}$,
Specific heat capacity of lead $=125\, J / kg K$ )

JEE MainJEE Main 2022Thermal Properties of Matter

Solution:

$m \times 125 \times 200+ m \times 2.5 \times 10^{4}=\frac{1}{2} mv ^{2} \times \frac{40}{100}$
$V =500 \,m / s$