Start by writing an equation for the position of each car at a
given time t. For the speeder, you can use x-final = x-initial +
v*t since he's moving at constant velocity. Let's put x-initial
at zero for both cars for simplicity. The speeder's position,
x1, is given by: x1 = 17.9t The police car has zero initial
velocity but is acceleration. So his equation of motion is given
by: x2 = (1/2)*(4.5)*t^2 The police car will catch the speeder
when x1 = x2. So set these two equations equal: 17.9t =
(1/2)*(4.5)*t^2 You can cancel out a t on each side since t=0 is
not the solution we want (it's when the car first passed the
police car) to so t = 2*17.9/4.5