Chapter 2449P24.72Consider the gaussian surface described in the solution to problem 71.(a)For xd>2,dqdVAdxCAx dx===ρρ2EA⋅=∈=∈=∈FHGIKJFHGIKJzzzddqEACAx dxCAdd11380020203ECd=∈3024orEiEi=∈>= −∈< −CdxdCdxd3030242242±;±for for (b)For −<<dxd22EA⋅=∈=∈=∈zzzddqCAx dxCAxx13002030EiEi=∈>= −∈<CxxCxx30303030±;±for for P24.73(a)A point mass mcreates a gravitational accelerationgr= −Gmr2±at a distance r.The flux of this field through a sphere isgA⋅= −= −zdGmrrGm2244ππej.Since the r has divided out, we can visualize the field as unbroken field lines. The same fluxwould go through any other closed surface around the mass. If there are several or nomasses inside a closed surface, each creates field to make its own contribution to the net fluxaccording togA⋅= −zdGm4πin.(b)Take a spherical gaussian surface of radius r. The field is inward sogA⋅=°= −zdgrgr
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