Question

If the ground is smooth, what is the total kinetic energy of the body after $2s$?

• A. $100J$
• B. $75J$
• C. $50J$
• D. $25J$

Answer 1

The correct option is C $50J$

Net force $=0\Rightarrow a_{net}=0$

Net torque about $o,\tau =F\left(2R\right)-F\left(R\right)$

$=FR$ [anti clock wise]

$\alpha =\frac{T_0}{I}=\frac{10\times 1}{4}=2.5$

$w_f=wi+\alpha t$

$w_f=0+2.5\times 2$

$w_f=5$

$KE=\frac{1}{2}{Iw}^2=\frac{1}{2}\times 4\times 5^2=50J$