Question

A lead bullet penetrates into a solid object and melts. Assuming that 50% of its kinetic energy was used to heat it, calculate the initial speed of the bullet. The initial temperature of the bullet is `27^@C` and its melting point is `327^@C`. Latent heat of fusion of lead `= 2.5 xx 10^4 J//kg` and specific heat capacity of lead `=125 J//kg.K`.
A. `100 m//s`
B. `500 m//s`
C. `800 m//s`
D. `1000 m//s`

Answer 1

Correct Answer - B
`(1)/(2)mv^2xx(1)/(2)=msDeltatheta+mL`
`(v^2)/(4)=125(327-27)+2.5xx10^4`
`=125xx300+2.5xx10^4`
`v=500 m//s`