*33.  mmh A car is traveling at 20.0 m/s, and the driver sees a traffic light turn red. After 0.530 s (the reaction time), the driver applies the brakes, and the car decelerates at 7.00 m/s2. What is the stopping distance of the car, as measured from the point where the driver first sees the red light?

 

We need to break this into two parts.  The driver will travel a distance while the reaction time is occurring.  For this part we have  , an acceleration  , and a time  .  The equation we should use is

 

So

 

Once the braking occurs and the car is under acceleration  (Note: - sign since we are braking), we still have  , we know  , and we are looking for stopping distance.  Use relationship

Solve for distance

 

So the total stopping distance is found by adding

 

 

 

 

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This page last updated on January 11, 2020