Laws of Motion

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Question : 31
Total: 40
A train runs along an unbanked circular track of radius 30 m at a speed of 54 km h1. The mass of the train is 106 kg. What provides the centripetal force required for this purpose? The engine or the rails? What is the angle of banking required to prevent wearing out of the rail?
Solution:  
Radius of circular bend, r = 30 m,
speed of train =v=54kmh1=54×
5
18
=15ms1
mass of train, m=106kg
angle of banking =θ=?
The centripetal force is provided by the lateral thrust by the rails on the wheels. According to Newton’s third law of motion, the train exerts an equal and opposite thrust on the rails causing its wear and tear.
The angle of banking is given by
tanθ=
v2
rg
=
(15)2
30×10
=
225
30×10
=0.75

θ=tan1(0.75)37°
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