position and movement

A car undergoes uniform decleration along a straight road,Its velocity decreases from 30ms^-1 after travelling a distance of 100m.How much further will the car travel before it comes to a rest?

A.50m

B.80m

C.180m

D.200m

E.300m

列算式thx

1 Answer

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  • 1 decade ago
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    You have some information missing. How much does its velocity decrease?

    As far as I remember this question, the velocity should decrease from 30 m/s to 20 m/s in 100 m.

    So, I will use this to do the question.

    Initial velocity, u = 30 m/s

    Final velocity, v = 20 m/s

    Distance, s = 100 m

    By v2 = u2 - 2as

    (20)2 = (30)2 - 2a(100)

    Deceleration, a = 2.5 ms-2

    Now, initial velocity, u = 20 m/s

    Final velocity, v = 0

    By v2 = u2 - 2as

    0 = (20)2 - 2(2.5)s

    Further distance, s = 80 m

    So, the answer is B.

    Source(s): Physics king
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