Physics Help Forum Electric force on a sphere
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 Sep 29th 2011, 04:46 PM #1 Junior Member   Join Date: Sep 2011 Posts: 1 Electric force on a sphere Problem: Two small plastic spheres each have a mass of 2.0 and a charge of -50.0. They are placed 2.0 apart. Question: By what factor is the electric force on a sphere larger than its weight? Weight= 19.6 N Electric Force would be = 8.99 x 10^9 * 5x10^-8/(.02)^2 Is this correct to begin? then how would I find the factor difference?
 Oct 3rd 2011, 12:35 AM #2 Physics Team     Join Date: Jun 2010 Location: Mauritius Posts: 609 Not quite, notice that the mass is in grams and not in kilograms But it's okay, now to get the factor, you are being asked how many times the electrostatic force is larger/smaller than the weight (or did the question mean the gravitational force and you understand it another way?). So, bring down the weight to 1. That is, by how much do you have to divide the weight for it to become equal to 1? When you have got that value, divide the electrostatic force by that same value, and that will be your answer. E.g. Weight = 5 N E. Force = 20 N Value to divide weight to get 1 is 5 (5/5 = 1) Thus, factor = (20/5 =) 4. So, the factor the electric force is 4 times larger than its weight. But I will say it again, are you sure it meant weight, or did it mean the gravitational attraction between the two spheres? __________________ Jerry (Got my results!) It is easier to protect your feet with slippers than to cover the earth with carpet. No one can go back and change a bad beginning; but anyone can start now and create a successful ending. If a problem can be solved, no need to worry about it. If it cannot be solved what is the use of worrying?

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