[SOLVED] Mechanical waves 1. The problem statement, all variables and given/known data Hi all. Please see the last page in this .ppt (problem 15.66): http://web.utk.edu/~kamyshko/P232/Problems_13_15.pdf 3. The attempt at a solution Here are my answers - I would be grateful, if you would read them through and comment/help where necessary: a) Since there are 5000 flashes/min, there's 83,3 flashes/s. I want to find the time it takes for 5 flashes, which is 5/83,3 = 0,06 s. This is the half of the period T (half the unit-circle?), so the period T = 2*0,06 s = 0,12 s. The frequency is T^(-1), and to find the wavelength, I will use that the string is fixed at both end and since the string is one wavelength long, we can use that the wavelength lambda = L. b) Since there is only one point not moving, it is the second harmonic (first overtone). c) To find the speed of the travelling waves, I use that v = lambda*f. d) To find the speed of point P at position 1, I differentiate y(x,t) w.r.t. t and insert x = L/4 (since P is at the top of the first crest so L/4 horizontal distance from starting point) and t = 0. To find the speed of point P at position 3, I do the same as above. e) To find the mass of the string, I use that v = sqrt(F/mju), where mju is mass/unit length. - Thanks in advance, sincerely Niles.