(1.a) The surface area being vibrated by the time the sound reaches the listener is 5,026.55 m².
(1.b) The intensity of the sound wave as it reaches the person listening is 0.02 W/m².
(1.c) The relative intensity of the sound as heard by the listener is 103 dB.
(2.a) The speed of sound if the air temperature is 15⁰C is 340.3 m/s.
(2.b) The frequency of the sound heard by the suspect is 614.3 Hz.
<h3>
Surface area being vibrated</h3>
The surface area being vibrated by the time the sound reaches the listener is calculated as follows;
A = 4πr²
A = 4π x (20)²
A = 5,026.55 m²
<h3>Intensity of the sound</h3>
The intensity of the sound is calculated as follows;
I = P/A
I = (100) / (5,026.55)
I = 0.02 W/m²
<h3>Relative intensity of the sound</h3>
<h3>Speed of sound at the given temperature</h3>
<h3>Frequency of the sound</h3>
The frequency of the sound heard is determined by applying Doppler effect.
where;
- -v₀ is velocity of the observer moving away from the source
- -vs is the velocity of the source moving towards the observer
- fs is the source frequency
- fo is the observed frequency
- v is speed of sound
Learn more about intensity of sound here: brainly.com/question/17062836
D. Using a fixed-pulley system
<span>The four goals of psychology are: describe observed phenomena, explain them, predict what may occur as a result of them and control behaviour as a result. Julie’s psychologist has helped Julie control her behaviour - her fear response to spiders - so they have met the ‘control behaviour’ goal of psychology.</span>
Firstly, we need to make the times and distance equal to compare.
1hr=60mins
Gonz drove 90km in 60mins,so they would drive 45km in 30 mins dividing it by 2.
Because the Rivs had gone 30km in 30mins, Gonz were faster.
For the adverage speed, we should first add the speed of each family in mph , so 90+60, which equals 150 and divide that by 2 because there are 2 speeds so the average speed is 75mph.
P.S English is my second language so tell me if you don't understand something and I will try and explain.
Answer:
Answer: It takes 5,730 years for half the carbon-14 to change to nitrogen; this is the half-life of carbon-14. After another 5,730 years only one-quarter of the original carbon-14 will remain
