Question

A solid sphere is in rolling motion. In rolling motion a body possesses translational kinetic energy $(K_t)$ as well as rotational kinetic energy , $(K_r)$ simultaneously. The ratio $K_t : (K_t + K_r)$ for the sphere is

• A. 2 : 5
• B. 7 : 10
• C. 10 : 7
• D. 5 : 7

Answer 1

Answer: (D)

5 : 7

Answer 2

$K_{t} = \frac{1}{2} mv^{2}$
$K_{t} +K_{r} = \frac{1}{2} mv^{2} + \frac{1}{2} I \omega^{2} = \frac{1}{2} mv^{2} + \frac{1}{2} \left(\frac{2}{5} mr^{2}\right)\left(\frac{v}{r}\right)^{2}$
$= \frac{7}{10} mv^{2}$
So, $\frac{K_{t}}{K_{t} + K_{r} } = \frac{5}{7}$