Answer:
d. H + O2 ------ H2O
that's the formation of water
Answer:
false. it's positive terminal of an electric cell
E, B, C# minor and A for the most songs
A. 409 Hz
The fundamental frequency of a string is given by:

where
L is the length of the wire
T is the tension in the wire
m is the mass of the wire
For the piano wire in this problem,
L = 0.400 m
T = 1070 N
m = 4.00 g = 0.004 kg
So the fundamental frequency is

B. 24
For this part, we need to analyze the different harmonics of the piano wire. The nth-harmonic of a string is given by

where
is the fundamental frequency.
Here in this case

A person is capable to hear frequencies up to

So the highest harmonics that can be heard by a human can be found as follows:

Answer:
The vacuum tube was replaced with transistor.
Explanation:
- The invention of semiconductor was very useful in making solid state transistor that allowed the production of small yet faster, cheaper, and more trusted and reliable computers.
- These solid state transistor is so often used that, it nearly replaced all the use of transistor.
- This replacement took place after the invention of semiconductor in the year around 1940.
- Vacuum tubes also known as thermionic tubes are not used anymore in computers and electronics.