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Unformatted text preview: HPHY 253.02 Exam 02 (take-home) Spring Semester 2009 Dr. A. E. Bak Name Instructions. For each question, show all work leading to an answer and simplify as much as possible. 1. From Serway & Jewett Problem 25 : 7 . A block having mass m and charge + Q is connected to an insulating spring having force constant k . The block lies on a frictionless, insulating horizontal track, and the system is immersed in a uniform electric ¡eld of magnitude E directed as shown in Figure P 25 : 7 . The block is released from rest at a moment when the spring is unstretched (that is, when x = 0 ). (a) By what maximum amount does the spring expand? (b) What is the equilibrium position of the block? 2. Consider a closed surface S in a region of gravitational ¡eld g . Gauss¢s law for gravitation tells us that the gravitational £ux through surface S is linearly proportional to the total mass m in occupying the volume contained by S . More speci¡cally, Gauss¢s law states that I S g & da = ¡ 4 &Gm in : Note that g here is the total gravitational ¡eld, due to mass sources both inside and outside S . The value of G , the gravitational constant, is about 6 : 673 ¢ 10 & 11 N & m 2 =kg 2 . (a) Earth¢s volume mass density, at any distance r from its center, is given approximately by the function ¡ = A ¡ Br=R , where A = 1 : 42 ¢ 10 4 kg=m 3 , B = 1 : 16 ¢ 10 4 kg=m 3 , and Earth¢s radius R = 6 : 370 ¢ 10 6 m . Calculate the numerical value of Earth¢s mass....
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This note was uploaded on 05/01/2011 for the course HPHY 253 taught by Professor Bak during the Spring '09 term at Morehouse.
- Spring '09