Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason 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 R: The maximum potential energy of a body is zero when it is projected to infinity from earth surface.

• A. A False but $\mathbf{R}$ is true
• B. Both $\mathbf{A}$ and $\mathbf{R}$ are true and $\mathbf{R}$ is the correct explanation of $\mathbf{A}$
• C. $\mathbf{A}$ is true but $\mathbf{R}$ is false
• D. Both $\mathbf{A}$ and $\mathbf{R}$ are true but $\mathbf{R}$ is NOT the correct explanation of $\mathbf{A}$

Hint:

The kinetic energy needed to project a body to infinity is equal to the potential energy at the earth's surface.

Answer 1

The Correct Option is A

1. Assertion A: - The kinetic energy needed to project a body of mass $m$ from earth surface to infinity is $\frac{1}{2} \mathrm{mgR}$. 
- This is incorrect. 
2. Reason R: - The maximum potential energy of a body is zero when it is projected to infinity from earth surface. 
- This is correct. 
Therefore, the correct answer is (1) A False but $\mathbf{R}$ is true.