Air is a mixture.
as per definition, mixture is a combination we get after adding two or more things together in any proportion.
air is a mixture because it contains a number of gases like nitrogen , oxygen, carbon dioxide. it also contains dust particles, small organisms, water vapors etc.
carbon monoxide is not a mixture as it is formed from fixed proportion of carbon and oxygen.
similarly, water is is not a mixture as it is formed from fixed proportion of hydrogen and oxygen.
Answer: They’d fall at the same speed, because air resistance is the only thing that makes an object fall faster than another. There’s a video somewhere on the internet of a bowling ball and a feather falling at the same speed in a vacuum, if you look for it. Hope this helps!
Answer:

The Magnitude of electric field is in the upward direction as shown directly towards the charge
.
Explanation:
Given:
- side of a square,

- charge on one corner of the square,

- charge on the remaining 3 corners of the square,

<u>Distance of the center from each corners</u>


∴Distance of center from corners, 
Now, electric field due to charges is given as:

<u>For charge
we have the field lines emerging out of the charge since it is positively charged:</u>

<u>Force by each of the charges at the remaining corners:</u>

<u> Now, net electric field in the vertical direction:</u>


<u>Now, net electric field in the horizontal direction:</u>


So the Magnitude of electric field is in the upward direction as shown directly towards the charge
.
You must find the component of the force before calculating
B.Speed of light
The speed of light is used as a reference and is 3x10^8 m/s no matter what.
Hope this helps :)