Consider a car moving along a straight horizontal road with a speed of 72 km/h. If the coefficient of static friction between road and tyres is 0.5, the shortest distance in which the car can be stopped is

Consider a car moving along a straight horizontal road with a speed of

1.	Consider a car moving along a straight horizontal road with a speed of 72 km/h. If the coefficient of static friction between road and tyres is 0.5, the shortest distance in which the car can be stopped is
Answer» 30 m 40 m 72 m 20 m Solution :INITIAL KINETIC energy of the car = `1/2 mv^2` Work done against FRICTION = `mu mg s` From work - energy theorem `mu m g s = 1/2 mv^2 " or " s = ((V^2)/(2 mu g))` Stopping distance , `s = ((v^2)/(2 mu g))` Given, `v = 72 km//h = 72 xx 5/18 = 20 m//s` `mu = 0.5 and g = 10 ms^(-2)` `:. s = (20 xx 20)/(2 xx 0.5 xx 10) = 40 m` .