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 = 2.5×104 J/kg and specific heat capacity of lead = 125 J/kg⋅K .