How does the gravitational field strength g vary inside a uniform solid sphere of radius R at distance r from the centre (r < R)?
Answer and explanation
Correct answer: D. It is directly proportional to r
- Step 1: By Gauss's law for gravity, only mass inside radius r exerts net gravitational force. Step 2. Enclosed mass M_enc = M (r/R)^3. Field g = G M_enc / r^2 = G M r / R^3, proportional to r. Answer: It is directly proportional to r. Why not the others: The field is zero only at the exact center (r = 0) and outside a hollow shell.
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