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NEET-XII-Physics
11: Gravitation
- #10Two concentric spherical shells have masses M1, M2 and radii R1, R2 (R1 < R2). What is the force exerted by this system on a particle of mass m1 if it is placed at a distance (R1 + R2)/2 from the centre?Ans : Consider that mass m is at a distance `` \frac{{R}_{1}+{R}_{2}}{2}`` as shown in the figure.

The gravitational force of m due to the shell of M2 is zero, because the mass is inside the shell.
∴ Gravitational force due to the shell of mass M2 = `` \frac{G{M}_{1}m}{{\left({\displaystyle \frac{{R}_{1}+{R}_{2}}{2}}\right)}^{2}}=\frac{4G{M}_{1}m}{{\left({R}_{1}+{R}_{2}\right)}^{2}}``
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