JEE Mains · Physics · STD 11 - 7. gravitation
Given below are two statements: one is labelled as Assertion \(\mathrm{A}\) and the other is labelled as Reason \(\mathrm{R}\) Assertion A : The kinetic energy needed to project a body of mass m from earth surface to infinity is \(\frac{1}{2} \mathrm{mgR}\), where R is the radius of earth.
Reason \(\mathrm{R}\) : The maximum potential energy of a body is zero when it is projected to infinity from earth surface.
In the light of the above statements, choose the correct answer from the option given below
- A \(\mathrm{A}\) False but \(\mathrm{R}\) is true
- B Both \(\mathrm{A}\) and \(\mathrm{R}\) are true and \(\mathrm{R}\) is the correct explanation of \(\mathrm{A}\)
- C \(\mathrm{A}\) is true but \(\mathrm{R}\) is false
- D (4) Both \(\mathrm{A}\) and \(\mathrm{R}\) are true but \(\mathrm{R}\) is NOT the correct explanation of \(\mathrm{A}\)
Answer & Solution
Correct Answer
(A) \(\mathrm{A}\) False but \(\mathrm{R}\) is true
Step-by-step Solution
Detailed explanation
\(\mathrm{KE}=\frac{1}{2} \mathrm{~m}\left(\frac{2 \mathrm{Gm}}{\mathrm{R}}\right)=\mathrm{mgR}\) Assertion wrong at \(\infty\) \(\mathrm{U}=0\) \(\therefore\) Reason correct.
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