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A particle of mass 10 g is kept on the surface of a uniform sphere of mass 100 kg and radius 10 cm. Find the work to be done against the gravitational force between them to take the particle far away from the sphere. (you may take G = 6.67 × 10⁻¹¹ N m² / kg²)

1. 3.33 × 10⁻¹⁰ J
2. 13.34 × 10⁻¹⁰ J
3. 6.67 × 10⁻¹⁰ J
4. 6.67 × 10⁻⁹ J

Correct answer: 6.67 × 10⁻¹⁰ J

Solution

Work = G M m / R = (6.67e-11 * 100 * 0.010) / 0.10 = 6.67e-10 J.

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