19. A proton with speed v = 3.00×105m/s orbits just outside a charged sphere. The radius of the orbit is 1.0 cm. What is the charge on the sphere? (The mass of a proton is 1.67×10−27kg.)
(A)1.04×10−9C
(B)3.47×10−8C
(C)6.23×10−8C
(D)6.50×10−8C
(E)8.28×10−7C
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