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Unformatted text preview: 2Gauss’ law:1For gravity :r g ⋅dr A ∫ ∫= 4πGMenclosedFor electricity :r E ⋅dr A ∫ ∫=Qenclosed/ε22For the example of the uniform disk, could we have used Gauss’ law with the Gaussian surface depicted below?A)Yes, and it would have made the problem much easier!!!B)Gauss’ law applies, but it would not have been usefulto compute “g”C)Gauss’ law would not even apply in this caseGaussian surface:Flat, massive, uniform diskConsider a thin cylindrical shell that has a uniform mass per unit area of σ. If we want to find the gravitational force on an object a an arbitrary position on the zaxis, can we use Gauss’ Law?A)Of course, and it makes the problem simple since it has cylindrical symmetryB)Gauss’ law is valid, but not helpfulC)Gauss’ law is not valid hererz24Consider these four closed gaussian surfaces, each of which straddles an infinite sheet of constant areal mass density. The four shapes are I: cylinderII: cubeIII: cylinder IV: sphere For which of these surfaces does gauss's law, hold ? A)All B) I and II only C) I and IV only D) I, II and IV onlyE) Some other combor g ⋅dr A ∫ ∫= 4πGMenclosed25Consider these four closed gaussian surfaces, each of which straddles an infinite sheet of constant areal mass density. The four shapes are I: cylinderII: cubeIII: cylinder IV: sphere For which of these surfaces does gauss's law, help us find g near the surface??...
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 Spring '11
 STEVEPOLLOCK
 Gauss' Law, General Relativity, mass density

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