Question

1. Use the equation yetar(x.0 - 2A cos(cos(x-ot +) to determine the initial displacement of the total wave when (a) ф-: 0 (b) ф з (c) ф-2 (d) ф :IT (e) ф-300"(f) ф-270" 2. (a) What is the relationship between sound level, energy, power and intensity? would the intensity of a sound heard by a listener be reduced if the listener moved three times further away from the source? 9 (b) By what proportion 3. For a standing wave on a string that is fixed at both ends, both of the ends will be nodes. Draw a diagram of a standing wave in fifth mode. Label the nodes and antinodes. How many nodes are there in the fifth mode? How many antinodes are there? 4. (a) Assuming that sound travels at 343 m/s determine the distance that a sound wave travels in 4.6 s. (b) What factors might affect the propagation speed of sound in air? 5. (a) Given that the bulk modulus of water is 2.15 x 10 N/m2 and water has a density of 1.00 g/em then what is the speed of sound in water? (b) Does sound travel faster in air or in water? Why? 6. The wavelike motion o digestive track muscles is called peristalsis. Suppose a peristaltic wave in the small intestine lasts for only 13.5 s and the wave travels at a speed of only 3.56 cm/s. Determine the wavelength of the digestive wave. (Express the answer in both cm and m) 7. A wave on a string has a propagation speed of 27 m/s. Given that the frequency is 16 Hz determine (a) the period (b) the angular frequency (c) wavelength (d) and the angular wave number.

Answer 1

4.

a)

V = sound velocity = 343 m/s

t = time taken = 4.6 s

distance travelled is given as

d = V t

d = (343) (4.6)

d = 1577.8 m

b)

the speed of sound change due to change in the medium.

7.

a)

v = speed = 27 m/s

f = frequency = 16 Hz

a)

period is given as

T = 1/f

T = 1/16 = 0.0625 sec

b)

angular frequency is given as

w = 2 $\pi$ f = 2 x 3.14 x 16 = 100.5 rad/s

c)

wavelength is given as

$\lambda$ = v/f

$\lambda$ = 27/16 = 1.6875 m

d)

angular wave number is given as

k = 2 $\pi$ / $\lambda$

k = 2 (3.14)/1.6875 = 3.72