In proton-beam therapy , a high-energy beam of protons is fired at a tumor. The
ID: 1539902 • Letter: I
Question
In proton-beam therapy, a high-energy beam of protons is fired at a tumor. The protons come to rest in the tumor, depositing their kinetic energy and breaking apart the tumor’s DNA, thus killing its cells. For one patient, it is desired that 0.10 ( m J) of proton energy be deposited in a tumor. To create the proton beam, the protons are accelerated from rest through a 20 ({ m ; MV}) potential difference.
Part A
What is the total charge of the protons that must be fired at the tumor to deposit the required energy?
Express your answer to two significant figures and include the appropriate units.
(q) =
Explanation / Answer
one joule is gained when one coulomb passes through one volt.
Energy = Coulombs * Volts
q = E/V
q = 0.1 miliJoule / 20 MegaVolt
q = 0.0001/ 20000000
q = 5 x 10-12 C