Question

A solid sphere of mass $5kg$ rolls on a horizontal surface without slipping. If speed of its centre of mass is $4m{s}^{-1}$, its kinetic energy is:

• A. $65J$
• B. $56J$
• C. $28J$
• D. $33J$

Answer 1

The correct option is B $56J$

$m=5Kg$
Total $KE=\frac{1}{2}m{V}^2+\frac{1}{2}\left(\frac{2}{5}m{R}^2\right){\left(\frac{V}{R}\right)}^2$
$=\frac{1}{2}\times \frac{7}{5}m{V}^2$
$=\frac{7}{10}\times 5\times 4^2$
$=56J.$