Why is plasma called the "fourth state of matter"? i've recently heard that plasma is sometimes referred to as the "fourth state of matter". why is this? why is it not the first, second or third?

The two stars in a certain binary star system move in circular orbits. the first star, alpha, has an orbital speed of 36 km/s. the second star, beta, has an orbital speed of 12 km/s. the orbital period is 137 d. a) what is the mass of the star alpha? b) what is the mass of the star beta?

How do you know how many valence electrons an atom has?

The applied force of 3 washers will increase the applied force on the car to n.