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!

Linear motion

  1. Jul 1, 2010 #1
    1. The problem statement, all variables and given/known data

    A particle moves along the positivex-axis .At time t seconds after leaving a fixed point O from rest, the displacement of the particle from O is x cm. The acceleration, a of the particle is defined by

    a=5-3t , 0<=t<=1

    =-(4t+1), t>1

    Find the speed of the particle when x=2.5

    2. Relevant equations



    3. The attempt at a solution

    Integrate twice to get the displacement function,

    x=5t^2/2-t^3/2 , 0<=t<=1

    = -2/3t^3-2t^2 ,t>1

    so 5t^2/2-t^3/2=2.5

    solving this does not give me the answer. Where have i gone wrong?
     
  2. jcsd
  3. Jul 1, 2010 #2
    ur mistake is u considered only one condition thus u integrated only for 0<=t<=1. How r u sure u that at the time the particle will be at x=2.5 will be less than or equal to 1s. In fact if u do some calculation u will find its not true. thus u have to apply the second condition for t.
     
  4. Jul 1, 2010 #3
    But even when i considered the other one, i don get the answer too which is 1.5m
     
  5. Jul 1, 2010 #4
    actually u have to apply both integrating part by part.
     
  6. Jul 1, 2010 #5
    sorry but i don get what u mean
     
  7. Jul 7, 2010 #6
    any other insights to this problem?
     
  8. Jul 7, 2010 #7
    The way I see your work, in the 2nd integration to find x of t>1s, you set the lower limits as x=0 and t=0, right? Have it checked. That's wrong. Remember that you are considering t>1s; t=0 doesn't fit.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Linear motion
  1. Linear motion (Replies: 1)

  2. Linear motion (Replies: 1)

  3. Linear motion (Replies: 1)

  4. Linear Motion (Replies: 46)

Loading...