In proton-beam therapy, a high-energy beam of protons is fired at a tumor. The p
ID: 1448694 • 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 J of proton energy be deposited in a tumor. To create the proton beam, the protons are accelerated from rest through a 18 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? (with units please)
Explanation / Answer
Work done by the potential difference to get 0.1 J of Kinetic energy
W = q*V = 0.5*m*v^2 = 0.1 J
charge q = 0.1/V =0.1/(18*10^6) = 5.55*10^-9 C