I have problem solving this question on waves and sound test.?

Question

http://i39.photobucket.com/albums/e155/rhinotillexomania012/scan-3.jpg

Answer 1

17. The wavelength is the length of 1 cycle (2 loops). Thus, if there are 4 loops, then the wavelength is half the length of the string:
1.2m * .5 = .6 m

18. The relationship between wavelength, velocity, and frequency is defined as λ = v/f.
.6 m = v / 120 Hz
v = .6 m * 120 Hz
v = 72 m/s

19. If the speed increases with increased tension, then the weight should be increased. Tension is the force being directed along the string.

20. If the total vertical movement is 4 cm, then the amplitude is half that (it's only the distance from the middle to the extreme). 4 cm * .5 = 2 cm