40 answer a. s.a. p!

which choice best represents the sound waves from a soft low-pitched train rumble that suddenly shifts to a loud, high-pitched squeal of brakes?

a)

b)

c)

d)

At very high pressures, gases become and will eventually a) more dense; become hotter b) more dense; change to a liquid or solid c) less dense; combust d) less dense; turn into a liquid

You can decrease the resistance of a length of wire by

Two identical stars with mass m orbit around their center of mass. each orbit is circular and has radius r, so that the two stars are always on opposite sides of the circle. (a) find the gravitational force of one star on the other. (b) find the orbital speed of each star and the period of the orbit. (c) how much energy would be required to separate the two stars to infinity?