Heat is equivalent to which of the following quantities?
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−1 and specific heat capacity of lead = 125 J kg−1 K−1.
A lead ball at 30 ∘C is dropped from a height of 6.2 km. The ball is heated due to the air resistance and it completely melts just before reaching the ground. The molten substance falls slowly on the ground. Calculate the latent heat of fusion of lead. Specific heat capacity of lead = 126 J kg−1 ∘C−1 and melting point of lead = 330 ∘C. Assume that any mechanical energy lost is used to heat the ball. Use g = 10 ms−2.
2.4 × 104 cal/kg
2.4 × 104 J/kg
2.4 × 105 cal/kg
4.4 × 105 J/kg