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18. II In proton-beam therapy, a high-energy beam of protons is BIG red at a tumor. As the protons stop in the tumor, their kinetic energy breaks apart the tumor's DNA. thus killing the tumor cells. For one patient, it is desired to deposit 0.10 J of proton energy in the tumor. To create the proton beam. protons are accelerated from rest through a 10,000 kV potential difference. What is the total charge of the protons that must be red at the tumor? 20. II Physicists often use a different unit of energy, the electron volt, when dealing with energies at the atomic level. One electron volt, abbreviated eV, is defined as the amount of kinetic energy gained by an electron upon accelerating through a 1.0 V potential difference. a. What is 1.0 electron volt in joules? b. What is the speed of a proton with 5000 ev of kinetic energy?33. II A 2.0 nC charge: and a +2.0 nC charge are located on the x-axis at x = 1.0 cm and x = +1.0 cm. respectively. at. Other than at infinity. is there a position or positions on the xaxis where the electric field is zero? If so. where? b. Other than at infinity, at what position or positions on the x-axis is the electric potential zero? c. Sketch graphs of the electric field strength and the electric potential along the xaxis. 59. || One form of nuclear radiation. beta decay. occurs when a neutron changes into a proton. an electron. and a neutral particle called a neutrino: n p" + e" + v where v is the symbol for a neutrinO. When this change happens to a neutron within the nucleus of an atom, the proton remains behind in the nucleus while the electron and neutrino are ejected from the nucleus The ejected electron is called a beta particle. One nucleus that ex- hibits beta decay is the isotope of hydrogen 3H. called tritium, whose nucleus consists of one proton (making it hydrogen} and two neutrons (giving tritium an atomic mass m = 3 u). Tritium is radioactive. and it decays to helium: 3H r 3He + e" + v. a. Is charge conserved in the beta decay process? Explain. h. Why is the final product a helium atom? Explain. c. The nuclei of both 3H and 3He have radii of [.5 X Ill'5 in. With what minimum speed must the electron be ejected if it is to escape from the nucleus and not fall back? \f