Constant Acceleration of a motorist

[devyn]

Homework Statement

A speeding motorist traveling 120 km/h passes a stationary police officer. The officer <i>immediately</i> begins pursuit at a constant acceleration of 10.0 km/h/s. How much time will it take for the police officer to reach the speeder, assuming that the speeder maintains a constant speed? How fast will the police officer be traveling at this time?

Homework Equations

These are the equations we have to pull from in class:

V_f=V_i + at
D= V_it + 1/2at²
D=1/2t (V_f+V_i)
V_f²=V_i² + 2aD

The Attempt at a Solution

I fixed the mixed units so that 120 km/h equals 33.33 m/s and 10 km/h/s equals 2.778 m/s²
The officer's Vi is 0.
Distance(D) of the motorist and Distance(D) of the officer should be the same, as well as their times(t).
So, D_m=D_o
and t_m=t_o
I've tried solving the above equations for a distance or a time that i can then sub back in, but nothing seems to be working. I just need a little push in the right direction.

 

[LowlyPion]

Write equations for motorist and officer starting at t=0 and apparently x=0 for each.

When the X's equal then the motorist gets his ticket.