# The minimum stopping distance for a car traveling at a speed of 30 m/s is 60 m, including the distance traveled during the driver's reaction time of 0.60s . What is the minimum stopping distance...

The minimum stopping distance for a car traveling at a speed of 30 m/s is 60 m, including the distance traveled during the driver's reaction time of 0.60s .

What is the minimum stopping distance for the same car traveling at a speed of 34m/s ?

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### 1 Answer

Stopping Sight Distance(SSD)

Braking Distance(BD)

Reaction Distance(RD)

`SSD = RD+BD`

When the driver see a objection it gets some time for him to identify and confirm there is a threat. Once he realized the threat he will start to brake.There is a small time gap between the vision of the threat and initiating of brakes. In this time the vehicle travels in its speed. This is what you call by distance travel in reaction time.

In this case distance travel in reaction time is 30xx0.6 = 18m

Let us assume that in both cases once the driver applied brakes the vehicle experience constant deceleration.

Using equations of motion;

`v^2 = u^2+2aS`

`a = (v^2-u^2)/(2S)`

For case 1

`a = (0-30^2)/(2xx(60-RD))`

Since RD = 18m;

`a = (-900)/(2xx42)`

For second 2;

`a = (0-34^2)/(2BD)`

`BD = 34^2/2xx(2xx42)/900`

`BD = 53.95m`

`SSD = RD+BD = 18+53.95 = 71.95m`

*So minimum stopping sight distance at 34m/s speed is 71.95m.*

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