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Unformatted text preview: maini (nm7637) hw2 Shneidman (12108) 1 This print-out should have 7 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Forces between two objects which are in- versely proportional to the square of the dis- tance between the objects include which of the following? I) Gravitational force between two celestial bodies II) Electrostatic force between two electrons III) Nuclear force between two neutrons. 1. II and III only 2. III only 3. I only 4. I and II only correct 5. I, II, and III Explanation: I) Gravitational force 1 r 2 . II) Electrostatic force 1 r 2 . III) The nuclear force is very strong com- pared to the gravitational force and electro- static force over a very short range; outside of that range, however, it is negligible and cannot be proportional to 1 r 2 002 10.0 points Two identical small charged spheres hang in equilibrium with equal masses as shown in the figure. The length of the strings are equal and the angle (shown in the figure) with the vertical is identical. The acceleration of gravity is 9 . 8 m / s 2 and the value of Coulombs constant is 8 . 98755 10 9 N m 2 / C 2 . . 2 5 m 4 . 03 kg . 03 kg Find the magnitude of the charge on each sphere. Correct answer: 5 . 27508 10 8 C. Explanation: Let : L = 0 . 25 m , m = 0 . 03 kg , and = 4 . L a m m q q From the right triangle in the figure above, we see that sin = a L . Therefore a = L sin = (0 . 25 m) sin(4 ) = 0 . 0174391 m . The separation of the spheres is r = 2 a = . 0348782 m . The forces acting on one of the spheres are shown in the figure below....
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This note was uploaded on 01/31/2011 for the course PHYS 111 taught by Professor Moro during the Spring '08 term at NJIT.
- Spring '08