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Need help w/ Acceleration problem

  1. Feb 5, 2007 #1
    1. The problem statement, all variables and given/known data

    A freight train has a speed of 28.7 m/s at a given instant and 10.8 seconds later its speed is 23.7 m/s. What is the train's acceleration?

    What additional time would be necessary to bring the train to a complete stop, if it continues to slow at the rate in the previous question?

    What total distance is travelled in stopping during the entire slowing phase?
  2. jcsd
  3. Feb 5, 2007 #2
    The average acceleration is given by the final velocity minus the initial velocity over the time, or (Vf - Vi)/t.

    The initial velocity, final velocity, and time are all directly given to you. That much i trust you can do on your own :smile:

    Now we need to see going at that rate, how long it will to slow down. Speaking more precisely, if you were to think of it as slowing down by that much once every second, how many times could you fit that into your speed (taking the final speed, as we've already taken out the first second). Ofcourse the deceleration is continuous, but that is a workable conceptual model.

    Lastly we must use one of newton's equations to find the total distance x. << detailed solution deleted by berkeman >>
    Last edited by a moderator: Feb 5, 2007
  4. Feb 5, 2007 #3


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    Staff: Mentor

    WHO -- please be careful not to do too much of the original poster's (OP's) work for them. Or task here on the PF is to provide hints and direction, and help the OP to learn how to solve the problem on their own.

    junes -- In order for us to provide you with help, you must show some of your own work. We do not provide homework solutions on the PF.

    Zero-point warnings issued to you both. Welcome to the PF, BTW! It's a great place when used correctly. o:)
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