A 1000-kg car traveling at 70 m/s takes 3 m to stop under full braking. the same car under similar road conditions, traveling at 140 m/s, takes ______________ m to stop under full braking.
We assume [tex]a=const[/tex] (acceleration is constant. We apply the equation [tex]v^2=v0^2+2as[/tex] where s is the distance to stop [tex]v=0(m/s)[/tex]. We find the acceleration from this equation [tex]a=-v0^2/(2s)=-70^2/(2*3) =-816.7 (m/s^2)
[/tex] We know the acceleration, thus we find the distance necesssary to stop when initial speed is [tex]v=140 (m/s)[/tex] [tex]s=-v0^2/(2a) =140^2/(2*816.7)=12 (m)[/tex]
