An automobile moves on a road with a speed of 54 km h^–1. The radius of its wheels is 0.45 m and the moment of inertia of the wheel about its axis of rotation is 3 kg m². If the vehicle is brought to rest in 15 s, the magnitude of average torque transmitted by its brakes to the wheel is : 

6.66 kg m²s^–2

Torque : \(\tau = I\alpha\)

\(\tau = I\frac{a}{r}\)

\(\tau = I\frac{v}{tr}\)

v = 54 x \(\frac{5}{18}\) m/s ; I = 3 kg m² ; t = 15 s ; r = 0.45 m

⇒ \(\tau = 6.66 kg m^2s^{-2}\)