1.) S and P waves, simultaneously radiated from the hypocenter of an earthquake, are received at a seismographic station 17.3 s apart. Assume the waves have traveled over the same path at speeds of 4.50 km/s and 7.80 km/s. Find the distance from the seismograph to the hypocenter of the quake. The text doesn't thoroughly explain how to do these types of questions. So, I can't even explain what I did, since i have no beginning point. 2.) Two waves in one string are described by y1 = 3cos(4x - 1.6t) y2 = 4sin(5x - 2t) Find superposition. The formula I have for the addition of two wave functions requires both functions to be sin and also for the amplitudes to be equal. So, I made y1 = 3sin(4x - 1.6 - pi/2). However, how do i deal with the uncommon bases? 3.) Two pulses travel on string are described as functions: y1 = 5 / ( (3x - 4t)^2 + 2) y2 = -5 / ( (3x + 4t - 6t^2) + 2) When will the two waves cancel everywhere? At what point to the two pulses always cancel? I noticed that that y2 is reflected on the x-axis, and has a phase constant. Also, it is moving to the left, while y1 moves to the right. Firstly, what are the conditions under which the waves will cancel everywhere? For two waves to cancel everywhere, would they not have to have equal phase constants (which these do not? Also, what are the conditions for the waves to cancel? I propose that the functions be added, and the values be found which would cause y to equal = 0. However, there is both x and t variables! Thank you for any help you can provide on this urgen issue.