Answer quick please!!

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?

Which of the following is not a physical property of mattera. melting pointb. heat of combustionc. viscosityd. boiling point

Ajoint produces movement when its angle decreases. which type of movement is it?