Three metal rods are located relative to each other as shown in Figure P17.71, where L1 + L2 = L3. The speed of sound in a rod is given by v = Y/P where P is the density and Y is Young€™s modulus for the rod. Values of density and Young€™s modulus for the three materials are P1 = 2.70 x 103 kg/m3, Y1 = 7.00 x 1010 N/m2, P2 = 11.3 x 103 kg/m3, Y2 = 1.60 x 1010 N/m2, P3 = 8.80 x 103 kg/m3, Y3 = 11.0 x 1010 N/m2.
(a) If L3 = 1.50 m, what must the ratio L1/L2 be if a sound wave is to travel the length of rods 1 and 2 in the same time as it takes for the wave to travel the length of rod 3?
(b) If the frequency of the source is 4.00 kHz, determine the phase difference between the wave traveling along rods 1 and 2 and the one traveling along rod 3.

L1 , Figure P17.71