Q.

A circular racetrack of radius 300 m is banked at an angle of 15°. The coefficient of friction between the wheels of a race car and the road is 0.2. The optimum speed of the race car to avoid wear and tear on its tyres is, the maximum permissible speed to avoid slipping is  (Take tan15°=0.27, g=10 m s-2)

1 18.6 m s-1  
2 28.6 m s-1  
3 38.6 m s-1  
4 48.6 m s-1  

Ans.

(3)

The maximum permissible speed is given by

vmax=Rg(μ+tanθ)1-μtanθ=300×10×(0.2+0.27)1-0.2×0.27=38.6 m s-1