A car moving aling a straight highway with speed of ` 126 km h^(-1)` is brought to a stop within a distance of ` 200 m`. What is the retardation of the car (assumed uniform ) ans how doest it take fro the car to stop ?

Explanation

Here, ` u= 126 h^(-1)` = ( 126 xx1000 )/( 60 xx 60)1 ms^(-1) =35 ms^(-1) , v=0. S = 200 m,a = ? And t= ?`
We know, `v^2 =u^2 a S :. 0= (35) ^2 + 2 xx a xx 200 or a=- ( 35)^2/( 2 xx 200) =- (49)/(16) = 3.06 ms^(-2)`
As, ` v= u + at :. 0=35 - ( (49)/(16))t or t= (350 xx 16)/*49) = 980)/7 = 11. 43 s`.