College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 36

An x-ray tube used for cancer therapy operates at 4.0 MV, with a beam current of 25 mA striking the metal target. Nearly all the power in the beam is transferred to a stream of water flowing through holes drilled in the target. What rate of flow, in kilograms per second, is needed if the rise in temperature ( T ) of the water is not to exceed 50°C