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JEE Mains · Physics · STD 11 - Gravitation
  • JEE Mains 2023
  • Medium
  • MCQ

An object is allowed to fall from a height \(R\) above the earth, where \(R\) is the radius of earth. Its velocity when it strikes the earth's surface, ignoring air resistance, will be :

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Answer & Solution

Correct Answer

(B) \(\sqrt{g R}\)

Step-by-step Solution

Detailed explanation

Loss in \(PE =\) Gain in \(KE\)

\(\left(-\frac{ GMm }{2 R }\right)-\left(-\frac{ GMm }{ R }\right)=\frac{1}{2} mv ^2\)

\(\Rightarrow v ^2=\frac{ GM }{ R }= gR\)

\(\Rightarrow v =\sqrt{ gR }\)

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