40. We are concerned with the charges in the nucleus (not the “orbiting” electrons, if there are any). Thenucleus of Helium has 2 protons and that of Thorium has 90.(a) Eq. 22-1 givesF=kq2r2=³8.99×109 N·m2C2´(2(1.60×10−19C))(90(1.60×10−19C))(9.0×10−15m)2=5.1×102N.(b) Estimating the helium nucleus mass as that of 4 protons (actually, that of 2 protons and 2 neutrons,
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