text: i need help w/ a physics problem.  it has to do w/ acceleration and velocity. i have the answer from the book. speedy sue, driving at 30.0 m/s, enters a one-lane tunnel. she then observes a slow moving van 155m ahead traveling at 5.00 m/s. sue applies her brakes but can accelerate only at -2.00 m/s2 because the road is wet. will there be a collision? if yes, determine how far into the tunnel and at what time the collision occurs.  the answer says that there will be a collision 212 m into the tunnel at 11.4 sec. use the formula:   distance = vt + 0.5 * at^2  the distance of the van from the entrance of the tunnel is dv = 5t + 155.  the distance of the car from the entrance of the tunnel is dc = 30t + 0.5 * 2(t^2).  the two collide when dv = dc  5t + 155 = 30t - t^2 t^2 - 25t + 155 = 0  use quadratic formula and you get   t = 11.4 and 13.6  there would be therefore be a collision at 11.4 seconds.  then use same formula to work out distance  dc = 30 * 11.4 - 1 * 11.4 * 11.4 dc = 212m  **phew.. i'm a bit rusty this morning**