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Homework Help: Velocity time problem

  1. Nov 15, 2012 #1
    1. The problem statement, all variables and given/known data
    A motorist starting a car from rest accelerates uniformly to a speed of V ms in 6 seconds. He maintains this speed for 50 seconds and then applies the brake sand decelerates uniformly to rest. His deceleration numerically equal to four times the initial acceleration. The total distance travelled is 1000 meters

    2. Relevant equations

    1) Sketch a vt graph for the journey
    2) calculate the time during which the deceleration takes place
    3) calculate value of v
    4) Calculate the initial acceleration.

    3. The attempt at a solution

    1) is straight forward
    2) a= 6/4 =1.5s
    3) can you use s= ut+ 1/2at^2?
    4) .?

    I struggle with these types of question so any help would be greatly appreciated,

  2. jcsd
  3. Nov 15, 2012 #2


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    Homework Helper
    Gold Member

    2) Agree.
    3) That is good one to use, but I think it might be easier to solve 4), a, first.
    4) Break the problem up into 3 time/distance zones. Looking at zone 1 (0<t<6) first, what would you get for v (at the 6-second point) in terms of a? What would you get for the distance travelled in zone 1, in terms of a, etc...
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