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Unformatted text preview: HPHY 253.02 Exam 02 (takehome) 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.
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