i need help on 2 physic problems..please!?

Question

1) A person wears a hearing aid, which makes a sounds louder by 30 dB.

This means the sound intensity is increased______times
This means the amplitude of the soundwave is increased _____times


2) A hand holding a rope moves up and down to create a transverse wave on the rope. The hand completes an oscillation in 1.9 s, and the wave travels along the string at 0.5 m/s. The amplitude of the wave is 0.05 m.

a.) Find the frequency at which the crests pass a given point in space.

b.) Find the distance between two adjacent crests on the wave.

c.) There is a blue spot drawn onto the rope with a magic marker. Find the distance this spot travels in one period.

Answer 1

1. a) The sound intensity is increased 1 000 times: I = 10^(30/10) = 10³ = 1 000.

     b) The soundwave amplitude is increased √1 000 = 31.623... times, since intensity is proportional to the square of the wave amplitude. Thus, wave amplitude is proportional to the square root of the intensity.

2. a) Frequency is the inverse of period: f = 1/T = 1/1.9 = 0.5236... Hz

     b) Wavelenght  λ = vT = v/f = 0.5 s × 1.9 m/s = 0.95 m

     c) By definition, after exactly one period, any point in the rope returns to its starting point; net displacement (a vector) is therefore zero. Distance travelled (which is a scalar quantity) is twice the amplitude, 0.1 m. I'm not really sure which of these two conceptually different quantities the problem is asking for.

Answer 2

For number one, remember how sound intensity and amplitude of the sound wave are related. Also as a reminder, remember that the decibel scale is logarithmic not linear. This means 20 dB is 10 times louder than 10 dB and 60 dB is 100000 times louder than 10 dB, it is based on powers of ten.

For number two, you are given period find frequency, how do they relate? Distance can be found from wave speed and period. Also if you travel with the blue dot, how far have you gone up and down (hint look at amplitude)?

Answer 3

How are you able to believe it is nine.two m/s^two???? I knew it used to be nine.eight seeing that I used to be 14 or anything... we consistently used to circular it as much as 10 so if it used to be nine.two we might circular it as much as nine so it doesnt make feel if its nine.two *punches Kevin* (to knock a few feel into you!! like an traumatic physics trainer I had stated....)