What is the distance required to stop (i. e., braking distance) of a passenger car when brakes are applied on a 2% downgrade if that vehicle is traveling at 40 mph

The value is  

Explanation:

From the question we are told that

 The gradient is  G   =  2% = 0.02

   The initial  speed of the vehicle is  u =  40 mph

Generally the breaking speed is mathematically represented as

Here    is equal to longitudinal friction coefficient which has a value of

So

=>  

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see earlier answer