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Two lead spheres of \({20}{c}{m}\) and \({2}{c}{m}\) diametre respectively are planet with centres \({100}{c}{m}\) apart. Calculate the attraction between them, given the radius of the Earth as \({6.37}\times{10}^{{{8}}}{c}{m}\) and its mean density as \({5.53}\times{10}^{{{3}}}{k}{g}{m}^{{-{3}}}\). Speciffic gravity of lead \(={11.5}\). If the lead spheres are replaced by bress sphere of the same radii, would the force of attraction be the same?


Here, \({r}_{{{1}}}={0.20}/{2}={0.1}{m}\),
Mass of first lead sphere, \({m}_{{{1}}}=\frac{{{4}}}{{{3}}}\pi{{r}_{{{1}}}^{{{3}}}}\rho'\)
We know that, \({g}=\frac{{{G}{M}}}{{{R}^{{{2}}}}}=\frac{{{G}}}{{{R}^{{{2}}}}}\times\frac{{{4}}}{{{3}}}\pi{R}^{{{3}}}\rho\)
or \({G}=\frac{{{3}{g}}}{{{4}\pi{R}\rho}}\)
Force of attraction between lead spheres will
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