1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Finding final velocity.

  1. Sep 28, 2011 #1
    1. Determine the acceleration of an object whose velocity is initially 24 cm/s and which accelerates uniformly through a distance of 66 cm in 3.8 seconds.




    2. s = (vf + v0) / 2 * t,



    3. I tried rearranging that formula but I got vf= 477.6. This just doesn't make any sense
     
  2. jcsd
  3. Sep 28, 2011 #2
    Didnt you just find the final velocity? they asked for acceleration, so you should be solving for that since you have the time. you can find out the acceleration
     
  4. Sep 28, 2011 #3
    I was saying that the vf being 477.6 doesn't make sense. Also, how can I find a with just t.
     
  5. Sep 28, 2011 #4
    Determine the kinematic equation that you would have to use.....

    Vf = Vi + at
    Delta x = .5(vf+vi)t
    Delta x = Vi(t)+.5a(t^2)
    Vf^2 = Vi^2 + 2a(delta x)

    Choose which one you would use, and solve for Vf.
     
  6. Sep 28, 2011 #5

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    You apparently interpreted the equation as being s = (vf + v0) / (2 * t)

    However the equation is equivalent to s = ((vf + v0) / 2) * t
     
  7. Sep 29, 2011 #6
    With uniform acceleration, can you say that average velocity * 2 = vf?

    Well I don't have acceleration. I was thinking I would use the second one, but I don't have vf. What is delta x?
     
    Last edited: Sep 29, 2011
  8. Sep 29, 2011 #7

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    You can find average velocity. From that and the initial velocity you can find final velocity. Then acceleration.
     
  9. Sep 30, 2011 #8
    I tried taking the equation s = .5(vo+vf)t and rearranging it to get vf, which got me 10.7 which can't be right. What is the delta x in those equations?

    I have initial velocity, which is 24 m/s. I have average velocity which is 17.36(Displacement / time). So, from here. What do I use?
     
  10. Sep 30, 2011 #9

    SammyS

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Gold Member

    vf = 10.737 m/s is about right.

    The initial velocity is greater than the average velocity, so the object is slowing down.

    Now find the acceleration.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Finding final velocity.
  1. Finding final velocity (Replies: 1)

  2. Finding final velocity (Replies: 2)

Loading...