Accordingto a FIR in police station, car A wassittingat rest waiting for a red light at a crossing when it was hit by an identical car B from rear side. Bothcars had their hand brakes on, and from their skid marks it is surmised that they skidded together about `6`m in the oriinal directionof travel before coming to reat. Assuming a stopping force of about `0.7` times the combined weights of the cars (that is, `mu=0.7`) what must have been the approximate speed of car B just before the collision ?
