A car moving with a speed of 40 km/hr comes to rest at a distance of 2 m after applying brakes. If the same car is moving with a speed of 80 km/hr, what is the minimum stopping distance?

Explanation

`u_(1)=40km//hr, v=0, s_(1)=2m`
`u_(1)=(40xx10^(3))/(3600)=(200)/(18)ms^(-1)`
`v_(1)^(2)=u_(1)^(2)+2as" "(v_(1)=0)`
`rArr u_(1)^(2)=-2as_(1)`
`rArr" "u_(1)^(2)=-2xxa xx 2`
`rArr" "=(u_(1)^(2))/(-4)=-(((200)/(18))^(2))/(4)=-(200)/(18)xx(200)/(18)xx(1)/(4)`
`rArr" "=-(1000)/(324)=30.864~31`
`rArr" "a=-31ms^(-2)`
`u_(2)^(2)=-2as_(2)`
`(u_(2)^(2))/(2a)=(u_(2)^(2))/(62)`
`s_(2)=(((400)/(18))^(2))/(62)`
`s_(2)=7.96m`