JEE Mains · Physics · STD 11 - 7. gravitation
The approximate height from the surface of earth at which the weight of the body becomes \(\frac{1}{3}\) of its weight on the surface of earth is \(..........km\) : [Radius of earth \(R =6400 \,km\) and \(\sqrt{3}=1.732]\)
- A \(3840\)
- B \(4685\)
- C \(2133\)
- D \(4267\)
Answer & Solution
Correct Answer
(B) \(4685\)
Step-by-step Solution
Detailed explanation
\(Mg ^{\prime}=\frac{ M }{3}\, g\) \(g ^{\prime}=\frac{ g }{3}\) \(g^{\prime}=g\left(\frac{R}{R+h}\right)^{2}=\frac{g}{3}\) \(\frac{R}{R+h}=\frac{1}{\sqrt{3}}\) \(h =(\sqrt{3}-1) \,R\) \(=(1.732-1) 6400\) \(h =4685 \,km\)
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