the answer is 0.284 lb/in3
Answer:
$175
Explanation:
Insurance premium is expressed as a rate $1000
($3.50 per $1000)
Therefore;
Annual premium= $50000x$3.50/$1000
= $175
Langerhans cells exist on the surface of the skin. They help to protect you by keeping dangerous microbes from entering your body. Langerhans cells do this in two very different ways: by protecting your skin from infection and also by stimulating allergic reactions.
A. The molecules start packed together very tightly in a solid. Then when it turns to water, the molecules can move around each other freely, but still contained. When water turns to vapor, the molecules are going crazy moving around. They are not contained at all and bounce of of each other freely.
b. The temperature rises. (ice turns to water at 33 degrees and water turns to vapor at 212 degrees)
The Doppler effect is the right concept to solve this problem. The Doppler effect is understood as the change in apparent frequency of a wave produced by the relative movement of the source with respect to its observer. Mathematically it can be described as,
![f = (1-\frac{v_0}{v})f_0](https://tex.z-dn.net/?f=f%20%3D%20%281-%5Cfrac%7Bv_0%7D%7Bv%7D%29f_0)
Here,
= Frequency of the sound from the Whistle
f = Frequency of sound heard
v = Speed of the sound in the Air
Replacing we have that
![1- \frac{v_0}{343} = \frac{20kHz}{21kHz}](https://tex.z-dn.net/?f=1-%20%5Cfrac%7Bv_0%7D%7B343%7D%20%3D%20%5Cfrac%7B20kHz%7D%7B21kHz%7D)
![\frac{v_0}{343} = 1-\frac{20}{21}](https://tex.z-dn.net/?f=%5Cfrac%7Bv_0%7D%7B343%7D%20%3D%201-%5Cfrac%7B20%7D%7B21%7D)
![\frac{v_0}{343} = \frac{1}{21}](https://tex.z-dn.net/?f=%5Cfrac%7Bv_0%7D%7B343%7D%20%3D%20%5Cfrac%7B1%7D%7B21%7D)
![v_0 = \frac{1}{21}(343)](https://tex.z-dn.net/?f=v_0%20%3D%20%5Cfrac%7B1%7D%7B21%7D%28343%29)
![v_0 = 16.33m/s](https://tex.z-dn.net/?f=v_0%20%3D%2016.33m%2Fs)
Therefore the minimum speed to know if the whistle is working is 16.33m/s