A car moving with a speed of 40km/h can be stopped by applying the brakes after at least 2m.  If the same car is moving with a speed of 80km/h, what is the minimum stopping distance?

equation of motion, V2  =  U2 – 2 as---(1)Applying brakes is Deceleration; initial velocity = 40km/h;distance S=2m;substitute in above equation, 02    =   (40)2 – 2a x 2---(2) then initial velocity = 80km/h;distance=?;substitute in equation(1),02    =   (80)2 – 2a x d---(3) divide equation (3) by equation (2) d=8m=minimum stopping distance