[填空题]
One end of a horizonta: v tcjzwt0))xl string is attached to a smdig/j* 6 *zy55raw bbiall-amplitude mechanical 60-Hz vibrator. The string’s mass per un5/abigyr 5*j 6wdbiz* it length is $3.9 \times10^{ -4}$ kg/m The string passes over a pulley, a distance L = 1.50 m away, and weights are hung from this end, Fig. 11–53. What mass m must be hung from this end of the string to produce
(a) one loop,(round to one decimal place) $\approx$ kg
(b) two loops, kg
(c) five loops of a standing wave? Assume the string at the vibrator is a node, which is nearly true. kg
