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Homework Help: Acceleration homework

  1. Jun 20, 2012 #1
    1. The problem statement, all variables and given/known data

    Ten seconds after starting from rest, a car with a mass of 1000kg is moving at 40m/s. The acceleration of the car is?

    2. Relevant equations

    F=ma or a=vf-vi/t

    3. The attempt at a solution

    I have m=1000kg

    I am not sure if d is 40m/s though or is the force?
    And with one of the formulas I picked I wouldn't be able to use 1000kg? I have a feeling that this problem requires two formulas.
  2. jcsd
  3. Jun 20, 2012 #2
    Re: Acceleration

    Just note that d is velocity of the car. The usual sign for velocity is u or v, and d or s is commonly used for distance/displacement.

    So now, your initial velocity is 0, as it started from rest. You also know the final velocity, and the time interval to attain this final velocity(assuming constant acceleration) So, finding the acceleration shouldn't be a problem if you use one of those relevant equations :wink: And yes, you don't necessarily need the mass here. It can be used to calculate the force, but that doesn't concern the question....
  4. Jun 20, 2012 #3

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Acceleration

    All that is required is the basic definition of acceleration, which is the second equation you listed under 'relevant equations'.
  5. Jun 20, 2012 #4
    Re: Acceleration

    Ah ok. I dislike when there is extra information or too little, I know it's how they try to mess you up. It makes me nervous as well thinking that there may be a formula that I don't know. But should. It's easier with too little information though.

    Thank you.
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