1. A stretched string is vibrating in resonance with a driver at 450 Hz. The string is in its 5th harmonic mode. If the string is 1.75 meters long, has a mass of 3 grams, the tension in the string must be A. 120 N B. 170 N C. 255 N D. 510 N 2. A train coming toward you (you are stationary) blows a steady tone whistle that sounds like 800 Hz but as it passes you the pitch seems to drop to 700 Hz. How fast is the train moving to nearest m/sec A. 23 B. 26 C. 20 D. 24