# E1 - Phy sics 7B WS E1(rev 3.0 Page 1 E-1 Coulombs Law...

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Physics 7B WS E1 (rev. 3.0) Page 1 E-1. Coulomb’s Law Questions for discussion 1 . Coulomb’s Law for the electrostatic force between two point charges is F = qQ 4 "# 0 r 2 . ( ε 0 is constant, equal to 8.85 × 10 -12 C 2 /N m 2 , which determines the relative strength of the electric force. Some texts use the constant k C = 1/4 πε 0 , called Coulomb’s constant instead, which makes Coulomb’s Law look even more like Newton’s law of gravitation!) This looks a lot like Newton’s law for the gravitatational force between two point masses: F = G mM r 2 . And indeed, because both forces are “1/r 2 forces,” there are some mathematical similarities between them. However, all similarities aside, can you think of any important differences between electrostatic forces and gravitational forces? 2 . Two point charges q 1 = +2 C and q 2 = -3 C are fixed in place along the x-axis, as shown. You have in your hand another point charge q, and you want to place it somewhere on the x-axis. But you want to place it at a point where it will stay . That is, you want to place it at a point where it will feel no force due to the fixed charges q 1 and q 2 . (Hint: Think about what the force looks like

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## This note was uploaded on 11/19/2010 for the course LECTURE 1 taught by Professor Yildiz during the Fall '10 term at Berkeley.

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E1 - Phy sics 7B WS E1(rev 3.0 Page 1 E-1 Coulombs Law...

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