[问答题]
The two pulses shown in g ri ps/xb 4a0gsd1-) x(;trdmFig. 11–52 are moving toxt4q fcxf2y6 2l(.qw zward each other. (a) Sketch the shape of the string at the moment they directly overlap. (b) Sketch the shape of the string a few moments later. (c) In Fig. 11–36aqzt6fq( f24.l2xycxw, at the moment the pulses pass each other, the string is straight. What has happened to the energy at this moment?