※ 引述《enterNTU (發發)》之銘言：
: Car B is traveling a distance  d ahead of car A.
: Both cars are traveling at 20 m/s when the driver of B suddenly
: applies the brakes,causing his car to decelerate at 4 m/s^2 .
: it takes the driver of A 0.75 second to react. when driver of A
: applies his brakes,he decelerates at 5 m/s^2. determine the distance d
: between the cars so as to avoid a collision.
:  car A |...............| car B   ..............||
:                d


For car A,
Reaction distance r  = reaction time * speed
                   A

    2     2
By v  = v   + 2a(x-x ) ,
         0          0

                       2     2
                      v  - v
                            0
Braking distance b  = ────
                  A      2a
　　　　　　　　　　　　　 A

Stopping distance s  = r  + b
                   A    A    A

For car B,

    2     2
By v  = v   + 2a(x - x ),
         0            0
                         2     2
　　　　　　　　　　　　v  - v
                              0　　
Stopping distance s  =  ────
                   B       2a
                             B

d = s  - s
     A    B


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代入數字後答案應該是5 m，看看對不對？

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