17.14. Set Up: Solve: (a) and (b) and 17.15. Set Up: The mass of a proton is and the charge of a proton is The distance from the earth to the moon is The electrical force has magnitude with The gravitational force has magnitude with Solve: (a) The number of protons in each box is The total charge of each box is The tension in the string must equal this repulsive electrical force. The weight of the box on earth is and the weight of the box on the moon is even less, since g is less on the moon. The gravitational forces exerted on the boxes by the earth and by the moon are much less than the electrical force and can be neglected. (b) Reflect: Both the electrical force and the gravitational force are proportional to But in SI units the coefficient k in the electrical force is much greater than the coefficient G in the gravitational force. And a small mass of protons contains a large amount of charge. It would be impossible to put 1.0 g of protons into a small box, because of the very large repulsive electrical forces the protons would exert on each other. 17.16. Set Up:
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Gravitational Force, Electric charge, Gravitational forces, Fundamental physics concepts, electrical force