College Physics with MasteringPhysics 7th Edition by Jerry Wilson,Anthony Buffa,Bo Lou

Exercise 43

A 0.030-kg lead bullet hits a steel plate, both initially at 20 °C. The bullet melts and splatters on impact. (This action has been photographed.) Assuming that 80% of the bullet's kinetic energy goes into increasing its temperature and then melting it, what is the minimum speed it must have to melt on impact