1. Limited time only! Sign up for a free 30min personal 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!

Homework Help: Average acceleration problem having trouble

  1. Sep 9, 2012 #1
    At a certain time a particle had a speed of 11 m/s in the positive x direction, and 1.3 s later its speed was 78 m/s in the opposite direction. What was the average acceleration of the particle during this 1.3 s interval?


    2. Relevant equations
    I have Vi=11m/s, Vf=78m/s and t=1.3 m/s


    3. The attempt at a solution
    My attempt at the solution has been the formula of (78-11)/1.3. This has gotten me the answer of 51.54 and I at am a real loss. I have read my book over and over and I juts need some guidance.
     
  2. jcsd
  3. Sep 9, 2012 #2
    At a certain time a particle had a speed of 11 m/s in the positive x direction, and 1.3 s later its speed was 78 m/s in the opposite direction. What was the average acceleration of the particle during this 1.3 s interval?

    a=(vi+vf)/t

    a=(11-78)/1.3

    a= -51.54 m/s2

    Your vf should have been -78 m/s since it was moving in the opposite direction.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook