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Velocity & acceleration

  1. Oct 8, 2008 #1
    velocity & acceleration!!

    A truck covers 45.0 m in 8.00 s while smoothly slowing down to final speed 2.60 m/s.

    a. the original speed?

    b. the acceleration?

    i have no idea how to do this
    i thought i would use this formula

    Vfinal = Vinitial + at.......but i need to know the acceleration which i do not know how to find
     
  2. jcsd
  3. Oct 8, 2008 #2

    LowlyPion

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    Re: velocity & acceleration!!

    Perhaps you can find a more appropriate equation that takes into account the time and distance and velocity?
    https://www.physicsforums.com/showpost.php?p=905663&postcount=2
     
  4. Oct 8, 2008 #3
    Re: velocity & acceleration!!

    well every equation i see..requires that you know the velocity and acceleration...which is what im trying to find

    the only equation i think i can use is the average velocity...which would just be

    45/8 = 5.625

    i dont see how this helps

    im totally lost
     
  5. Oct 8, 2008 #4

    LowlyPion

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    Re: velocity & acceleration!!

    Well what about this one?

    [tex]x = x_0 + v_0 t + (1/2) a t^2 [/tex]
     
  6. Oct 8, 2008 #5
    Re: velocity & acceleration!!

    yea i was thinking abt that one

    but wat would i put in for acceleration?!!?
     
  7. Oct 8, 2008 #6
    Re: velocity & acceleration!!

    Why don't you try using this formula[​IMG] and this formula [​IMG] together.

    In the first equation solve for Vo then plug that equation in the second equation. You see?
     
  8. Oct 8, 2008 #7

    LowlyPion

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    Re: velocity & acceleration!!

    Actually you should consider solving the second one first for acceleration.
    Then use the first to give you your final V.
     
  9. Oct 8, 2008 #8
    Re: velocity & acceleration!!

    Yea but if you do it that way, you still don't know Vo ? That's why I said solve for Vo and then plug in because then everything else can be filled in accept for a. then that's how you get acceleration.
     
  10. Oct 8, 2008 #9

    LowlyPion

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    Re: velocity & acceleration!!

    What if I said :
    The a would be the same magnitude but different sign.
     
  11. Oct 8, 2008 #10
    Re: velocity & acceleration!!

    Oh wow interesting never thought of it like that. true
     
  12. Oct 8, 2008 #11
    Re: velocity & acceleration!!

    wow..i would never have figured that out

    thanks a lot guys
     
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