A soccer player swings his leg forward to kick the ball. If his leg has a moment of inertia of 0.9 kg m2, and is initially at rest, how much torque must he generate with his hip flexor muscle in order to reach an angular velocity of - 8 rad/s in 0.5 seconds?

14.4 Nm

Explanation:

Moment of Inertia, I = 0.9 kg m^2, w0 = 0, w = 8 rad/s, t = 0.5 second

Use first equation of motion for rotational motion

w = w0 + α t

where, α be the angular acceleration

8 = 0 + α x 0.5

α = 16 rad/s^2

Now Torque = Moment of inertia x angular acceleration

τ = I x α

τ = 0.9 x 16 = 14.4 Nm