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# sol23 - 44 Electric forces are not important in determining...

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PHYSICS 103 Chapter 20 -- HW #23 Questions 34. Newton’s third law tells us that the force on object B is equal in magnitude and opposite in direction to the force on object A. Note that the charges on the two objects could be reversed without affecting the magnitude of the force. 40. The force on the charge at position A is zero. The left-hand charge repels the third charge pushing it to the right. The right-hand charge repels the third charge pushing it to the left. Because the charges are equal and the separations are equal, these two forces have the same size and therefore cancel. When the third charge is a position B, the left-hand charge pushes the third charge upward and to the right. The right-hand charge pushes the third charge upward and to the left. Because the charges are equal and the separations are equal, these two forces have the same size. Their horizontal components cancel and their vertical components add. Therefore, the net force acts up the page.
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Unformatted text preview: 44. Electric forces are not important in determining the motions in the solar system because of cancellation. Each of the bodies in the solar system has very nearly equal numbers of positive and negative charges. The attraction between the positive charges in one body for the negative charges in the other body is cancelled by the repulsion of the positive charge in the first body for the positive charges in the second, and so on. Because there is no cancellation with gravitational forces, they dominate at this scale. Exercise 8. The electric field is equal to the force a unit positive charge would experience at that place. We can get its value by dividing the force on a charged object by the charge on the object. The field doesn’t change if the object is removed. 3 3 75 N 5 10 N/C 15 10 C F E q-= = = - ×-× The minus sign indicates that the field points in the direction opposite to the force; that is, east....
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