Kinematics - linear motion?

A car is travelling at 13m/s towards some traffic lights. When the driver sees the lights change to red, the car is at a distance of 25m from the stop line. The reaction time of the driver is 0.7s and the condition of the road does not permit the car to decelerate greater than 4.5m/s/s. With brakes fully applied, how far from the stop line is the car when it stops? On which side of the line is the car?Kinematics - linear motion?Distance travelled with brakes on =%26gt; S1 = 13^2/2*4.5

Distance travelled during reaction time=%26gt; S2 = 13 *0.7



Total distance travelled =%26gt; S1+S2 = 28m



so the car is 28-25 = 3 m on the other side after crossing the lineKinematics - linear motion?If traveling at 13m/s, a 4.5/m/s2 deceleration would take you 2.9 seconds to stop. Assuming the deceleration is linear, you are traveling an average of 6.5m/s during that 2.9 seconds. That means the stop distance is 18.9 meters. That plus the 0.7 seconds of full 13m/s, which is 9.1 meters distance, would equal a total stop distance of 28 meters. Your car is over the line by 3 meters.