Question

A flywheel has an intial rotational kinetic energy equal to $10\text{J}$. A constant torque is applied on the flywheel and work done by the torque is $25\text{J}$. Find the final rotational kinetic energy of the flywheel.

• A. $15\text{J}$
• B. $25\text{J}$
• C. $35\text{J}$
• D. $0\text{J}$

Answer 1

The correct option is C $35\text{J}$

Given,
Initial rotational kinetic energy, $K{E}_1=10\text{J}$
Work done by the torque, $W=25\text{J}$
Let the final rotational kinetic energy $=K{E}_2$
By the work energy theorem for rotation.
Work done by the torque is equal to the change in rotational kinetic energy.
$W=K{E}_2-K{E}_1$
$\Rightarrow 25=K{E}_2-10$
$\Rightarrow K{E}_2=35\text{J}$