Does anyone know how to solve this?
A lorry travelling along a narrow road with speed u1 applies its brakes to give a uniform deceleration of magnitude a1. At the same time a car, a distance d behind the lorry and travelling in the same direction with speed u2, applies its brakes to give a uniform deceleration of magnitude a2.
Show that the car collides with the now stationary lorry if (a2) ≤ (ku2)^2, and find k in terms of u1, d and a1 .