A wheel with rotational inertia I is mounted on a fixed, frictionless axle. The angular speed ω of the wheel is increased from zero to ωf in a time interval T.
What is the amount of work done by the net torque to the wheel during this time interval?

A: [tex]\frac{1}{2}l\omega_{f}^{2}[/tex]
B: [tex]l\omega_{f} T[/tex]
C: [tex]l\omega_{f} ^{2}[/tex]
D: [tex]l\omega_{f} ^{2} /T[/tex]