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!

Wave question

  1. Feb 25, 2008 #1
    1. The problem statement, all variables and given/known data
    Two transverse waves are on the same piece of string. The first has displacement y non-zero only for kx + wt between pi and 2pi, when it is equal to Asin(kx + wt). The second has y = Asin(kx - wt) for kx - wt between -2pi and -pi, and is zero otherwise. When t=0, the displacement is such that there is a positive sinusoidal displacement between -2pi/k and -pi/k and a negative displacement between pi/k and 2pi/k. Calculate the energy of the two waves.

    What is the displacement of the string at t=3pi/2w? Calculate the energy at this time.


    2. Relevant equations



    3. The attempt at a solution

    OK so I did a kinda standard derivation for the energy in the string - for each wave, I did dKE = o.5pdx (dy/dt)^2 where the differential is a partial differential and p is the linear density of the string. I then integrated this over the lengths stated (pi/k to 2pi/k for the second wave). I did a similar thing for potential energy and got the total energy to be

    (pi/k)A^2 w^2 p

    First up I'm not sure if this is right, as there was no p stated in the question.

    For the next part, I think that at the time 3pi/2w, the two waves are about the origin and superimpose to produce a net displacement of zero - so what is the energy now? I assume it must be the same as I found no time or position dependence in the energy (and conservation of energy), but then where is the energy - surely there's no potential energy?

    Please help!
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you help with the solution or looking for help too?
Draft saved Draft deleted



Similar Discussions: Wave question
  1. Basic Wave question (Replies: 0)

  2. Wave Problem (Replies: 0)

  3. Velocity of a wave (Replies: 0)

  4. Wave Interference (Replies: 0)

Loading...