Discussion Questions
A The left panel of the figure shows a sequence of snapshots of two
positive pulses on a coil spring as they move through each other. In the
right panel, which shows a positive pulse and a negative one, the fifth
frame has the spring just about perfectly flat. If the two pulses have es-
sentially canceled each other out perfectly, then why does the motion pick
up again? Why doesn’t the spring just stay flat?
j/Discussion question A.
B Sketch two positive wave pulses on a string that are overlapping but
not right on top of each other, and draw their superposition. Do the same
for a positive pulse running into a negative pulse.
C A traveling wave pulse is moving to the right on a string. Sketch the
velocity vectors of the various parts of the string. Now do the same for a
pulse moving to the left.
D In a spherical sound wave spreading out from a point, how would
the energy of the wave fall off with distance?
Section 6.1 Free waves 359