In proton-beam therapy , a high-energy beam of protonsis fired at a tumor. The p
ID: 1668183 • Letter: I
Question
In proton-beam therapy, a high-energy beam of protonsis fired at a tumor. The protons come to rest in the tumor,depositing their kinetic energy and breaking apart thetumor’s DNA, thus killing its cells. For one patient, it isdesired that 0.10 J of proton energy be deposited in a tumor. Tocreate the proton beam, the protons are accelerated from restthrough a 11 MV potential difference. Question: What is the total charge of the protons thatmust be fired at the tumor to deposit the required energy? In proton-beam therapy, a high-energy beam of protonsis fired at a tumor. The protons come to rest in the tumor,depositing their kinetic energy and breaking apart thetumor’s DNA, thus killing its cells. For one patient, it isdesired that 0.10 J of proton energy be deposited in a tumor. Tocreate the proton beam, the protons are accelerated from restthrough a 11 MV potential difference. Question: What is the total charge of the protons thatmust be fired at the tumor to deposit the required energy? What is the total charge of the protons thatmust be fired at the tumor to deposit the required energy?Explanation / Answer
Provided information:Proton Energy = 0.10J Potential Difference = 11MV = 11 000 000V
E=qv
If the equation is rearranged for q:
q=E/v
The question provides the potential difference (E) and theproton energy (v) so sub 0.10J in for E and 11 000 000V in for v.This should provide the correct total charge of the protons thatmust be fired at the tumor to reach the needed energy level(q).
Note: When working with large numbers check that all theneeded significant digits are there. Sometimes calculators drop offdigits that could be needed to get the right answer.