1.

A car is travelling at a speed of 30 km per hour is brought to rest in a distance of 8 m by applying brake if the same car is moving at a speed of 60 m per hour then it can be brought to rest with the same braking

Answer»

u = 30 km/h = 30 *5/18 m/s


= 25/3 m/s


v = 0 m/s


s = 8 m


as v^2 - u^2 = 2 a s


so, 0 - (25/3)^2 = 2 a * 8


or, - 625/9 = 16 a


or, a = - 625/144 m/s^2


Now, u = 60 km/h = 60*5/18 m/s


= 50/3 m/s


v = 0 m/s


a = - 625/144 m/s^2


and v^2 - u^2 = 2 a s


so, 0- (50/3)^2 = 2(-625/144) s


or, 2500*144 / 9*2*625 = s


so, s = 32 m


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