1. Braking Distance

2.  The distance a car travels while it is trying to stop is called the braking or stopping distance.

3. Types of Tires

4. Braking Distance  The slope or grade of the road and the frictional resistance between the road and the car’s tires can affect the braking distance.

5.  Eg. Car with new tires on a dry, level road will have a shorter braking distance than one with worn tires on a wet road.

6. Explaining Breaking Distance  Braking distance is proportional to the square of the velocity of the vehicle.  Eg. If you double your speed, the braking distance increases four times (2 ). If you triple your speed, your braking distance increases nine times (3 ).

7. Formula for Breaking Distance  Braking distance is also dependent upon the friction between the two surfaces. We account for the frictional effects by using a mathematical constant for different kinds of surfaces.  d = kv 2  d = braking distance  k = frictional constant (different for each surface)  v = velocity (m/s)

8. Types of Surfaces

9. Try an example…  Eg. Find the braking distance for a car with a velocity of 50 km/h on dry pavement.

10. Reaction Time  Calculations for braking distance are for ideal cases only. In reality the driver’s reaction time also plays a role.  Reaction Distance = velocity x time

11. Try an example…  Eg. A car is moving at 50 km/h on dry pavement. Suddenly, 34 m away, a small dog darts into the roadway. Typically the driver takes 1.5 seconds to react. What is the total reaction distance?

12. Try an example…  Eg. A car is moving at 50 km/h on dry pavement. Suddenly, 34 m away, a small dog darts into the roadway. Typically the driver takes 1.5 seconds to react. What is the total breaking distance?

13. Total Stopping Distance  Therefore, when looking at the length that it takes a car to come to a stop we must look at the reaction time of the driver, as well as the braking distance.  Total Stopping Distance = reaction distance + braking distance

14. Try an example…  Eg. A car is moving at 50 km/h on dry pavement. Suddenly, 34 m away, a small dog darts into the roadway. Typically the driver takes 1.5 seconds to react. What is the total stopping distance?