Q. An automobile moves on a road with a speed of 54 $kmh^{-1}$. The radius of its wheels is 0.45 m and the moment of inertia of the wheel about its axis of rotation is 3 $kgm^2$. If the vehicle is brought to rest in 15s, the magnitude of average torque transmitted by its brakes to wheel is :
A) 2.86 $kg\,m^2s^{-2}$
B) 6.66 $kg\,m^2s^{-2}$
C) 8.58 $kg\,m^2s^{-2}$
D) 10.86 $kg\,m^2s^{-2}$
Explanation
[Solution] v = 15 m/s, $\omega_0 = 15/0.45 = 100/3$ rad/s, $\alpha = \frac{100}{45}$ rad/s²; $\tau = I\alpha = 3 \times \frac{100}{45} = 6.66$. Answer (2).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.