© Copyright, Department of Physics, University of Illinois at Urbana-Champaign

Highway Patrol

Suppose you are driving on the interstate at 39 m/s (about 87 miles per hour) when you see a highway patrol car parked up ahead. You apply your brakes, decelerating at a constant rate of 2 m/s2 until you're reduced your speed to 29 m/s (roughly 65 miles per hour). You then maintain a constant speed of 29 m/s. You pass the patrol car 15 seconds after you initially applied the brakes and are relieved that he doesn't pull out after you. How far away was the highway patrol car when you first saw it?

x = meters