Question

The position of axis of rotation of a body is changed so that its moment of inerted decreases by 36%. The % change in the radius of gyration is

• A. decreases by 18%
• B. increases by 18%
• C. decreases by 20%
• D. increases by 20%

Answer 1

The correct option is C decreases by 20%

$K=\sqrt{\frac{I}{m}}$

MOI is decreases by $36\%$

so new MOI $=0.641$

$K^1=\sqrt{\frac{0.641}{m}}=0.8K$

$\%change=\frac{K-K^1}{K}\times 100$

$=20\%$

decreases by $20\%$

Hence,

option $\left(C\right)$ is correct answer.