Acar travels along a straight line at a constant speed of 63.0 mi/h for a distance d and then another distance d in the same direction at another constant speed. the average velocity for the entire trip is 31.5 mi/h. (a) what is the constant speed with which the car moved during the second distance d?

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?