Travelling wave: finding the velocity from displacement

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1. Feb 23, 2016

kamhogo

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Hi everyone. I have trouble finding the velocity of a travelling wave give some information about it's displacement. I am given D (x,t)= 1 cm if |x - 4t| <\= 1 &&&D (x,t) = 0 cm if |x - 4t| > 1. I don't know how to interpret these mathematical statements. I've been trying for 3 hours now :(. I have the feeling that it's simple but I simply don't get it. 1) Do they mean that the wave number k=1 and the angular frequency omega=4? ( Inferred from the formula D (x,t)= A cos ( kx +/- wt + phase constant). Does it also mean that the phase constant =0 rad? 2) Am I able to draw a snapshot or hiatory graph from these statements only? If so, can someone give me a hint as of how to proceed? 3) I am asked to find the velocity of the wave. Hint as of how to do that please? Thanks in advance for any help!

2. Feb 23, 2016

kamhogo

Sorry for the typos!

3. Feb 23, 2016

nasu

This is not a sine wave but a pulse. You cannot identify k and omega. But you don't need to.
You can draw the wave at t=0 (for example) and then at some other value of t. 1 second, maybe.
This will show you how the wave front travels.

4. Feb 24, 2016

kamhogo

Thank you! I drew the wave at t=0s and and at t=1s and found the the displacement over one second (velocity)!