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A planet of radius R = 10 1 × (radius of Earth) has the same mass density as Earth. Scientists dig a well of depth 5 R on it and lower a wire of the same length and of linear mass density 10 –3 kgm –1 into it. If the wire is not touching anywhere, the force applied at the top of the wire by a person holding it in place is (take the radius of Earth = 6 × 10 6 m and acceleration due to gravity on Earth is 10 ms –2 ).

1. 96 N
2. 108 N
3. 120 N
4. 150 N

Correct answer: 108 N

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