(a) What is the potential at each of the following distances from a charge of 2uC: a = 10cm and b = 50cm? (b) What is the potential difference between points a and b? (c) How much work is required to carry a 0.05uC charge from point b = 50cm to a = 10cm? (d) Suppose that a proton is released at a = 10cm. How fast will it be moving as it passes a point at b = 50cm?
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V = kq/r
Va = 9e9*2e-6/0.1 = 180kV
Vb = 9e9*2e-60/0.5 = 36kV
Vab = 180kV-36kV = 144kV
(c)
Wab = Vab*q = 144e3*0.05e-6 = 0.0072 = 7.2mJ
(d) Volts = Joules/Coulomb
KE = Vab*q
½mV² = 144e3*1.602e-19 = 2.307e-14---> V² = 2*Vab*q/m = 2*2.307e-14/1.67e-27 = (5.3e6)²