Answer:
All of the above
Explanation:
Astronomers use all of those measures to classify stars. If you want to look more into classifying stars, check out the Hertzsprung-Russel Diagram. It covers how to identify red giants, main sequence, dwarf stars, ect. Distance from earth is typically measured in light years. The color of stars generally determines how hot they are. (Blue stars are the hottest) Also, the parallax method is used to measure stars that are closer to earth. This method relies heavily on geometry though.
Hope this helped!
Answer:
The average force exerted on the window due to two snowballs is 6 N
Explanation:
Given:
Mass of snowballs 
Kg
Velocity of snowball 
For finding the average force,
Force is equal to the change in momentum,
Here, final velocity is zero so we write,
Where 
sec
N
Above value of force is due to one ball, but here given in question there are two ball,
N
Therefore, the average force exerted on the window due to two snowballs is 6 N
Answer:
The problem occurs with all spherical mirrors.
Spherical mirrors are practical up to about inches in diameter.
Reflecting telescopes use spherical mirrors for apertures up to about 4 ".
Larger aperture telescopes use parabolic mirrors to obtain sharp focus.
