Q
What is meant by banking, 4 soad?
nehat is the need for banking
a road? obtain expression for the
manimum speect with which a vehicle
can safely negotiate a
cwewed
road
banked at an angle ca
The cofficient of friction between the
neheel and the road is u.
Answers
Explanation:
Banking of road means raising the outer edge of the road with respect to inner edge so that the road makes an angle with the horizontal.
When a vehicle moves along a curve, the force of friction provides the necessary centripetal force. But this force has a limit = μmg.When the speed of the vehicle increases beyond this maximum value, the banking of roads is necessary so that the component of normal reaction of the road towards the centre provides the necessary centripetal force.
From the figure, for vertical equilibrium :
Total upwards force = total downwards force
Ncosθ=mg+fsinθmg=Ncosθ−fsinθ...(1)
As the forces Nsinθ,fcosθ provide the necessary centripetal force.
rmv2=Nsinθ+fcosθ...(2)
Thus dividing (2) by (1),
mgrmv2=Ncosθ−fsinθNsinθ+fcosθ
As f=μsN
Thus,
rgv2=cosθ−μssinθsinθ+μscosθ=1−μstanθtanθ+μs=1−tanλtanθtanθ+tanλ=tan(θ+λ)
v=rgtan(θ+λ) where tanλ=μ