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The radius of planet A is half the radius of planet B. If the mass of A is MA, what must be the mass of B so that the value of g on B is half that of its value on A? |
Answer» Data : RA = RB/2, gB = \(\frac{1}{2}\) gA, MB = ? \(g=\frac{GM}{R^2}\) ∴ gA = \(\frac{GM_A}{R^{2}_A}\) and gB = \(\frac{GM_B}{R^2_B}\) ∴ \(\frac{g_B}{g_A}=(\frac{M_B}{M_A})(\frac{R_A}{R_B})^2\) ∴ \(\frac{1}{2}(\frac{M_B}{M_A})(\frac{1}{2})^2\) = \(\frac{1}{4}(\frac{M_B}{M_A})\) ∴ \(\frac{M_B}{M_A}=\frac{4}{2}\) = 2 ∴ MB = 2MA. |
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