B. The relationship between voltage, current and resistance is V=IR where V is directly proportional (one increases, the other also increases) to I and R while I and R are indirectly proportional (one increases, the other decreases).
(a) Wavelength and frequency of a wave are related by the following equation:
![\lambda= \frac{v}{f}](https://tex.z-dn.net/?f=%5Clambda%3D%20%5Cfrac%7Bv%7D%7Bf%7D%20)
where
![\lambda](https://tex.z-dn.net/?f=%5Clambda)
is the wavelength
f is the frequency
v is the speed of the wave.
The speed of sound at room temperature is approximately
![v=343 m/s](https://tex.z-dn.net/?f=v%3D343%20m%2Fs)
, so we can find the wavelength corresponding to a frequency of
![f=20000 Hz](https://tex.z-dn.net/?f=f%3D20000%20Hz)
by using the previous relationship:
![\lambda= \frac{v}{f}= \frac{343 m/s}{20000 Hz}=0.017 m](https://tex.z-dn.net/?f=%5Clambda%3D%20%5Cfrac%7Bv%7D%7Bf%7D%3D%20%5Cfrac%7B343%20m%2Fs%7D%7B20000%20Hz%7D%3D0.017%20m%20%20)
(b) the lowest sound we can hear has a frequency of f=20 Hz. Using the same relationship we used in the previous part of the exercise, we can find the corresponding wavelength:
B. Frictional force is your answer :)
False you cant control the size of feet