Question

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)
Latenet heat of fusion of lead = 2.5×104 J kg−1,
Specific heat capacity of lead = 125 J/KgK)

• A. 125 ms-1
• B. 500 ms-1
• C. 250 ms-1
• D. 600 ms-1
• E. 300 ms-1

Answer 1

Answer: (B)

500 ms-1

Answer 2

the correct option is (B): 500 ms-1
$0.4\times\frac{1}{2}\,mv^2=mS(t_2-t_1)$
v=500