Which is true of a mechanical wave? It can travel in a vacuum.

Both sound and light are examples.

It must travel in empty space.

It must have a medium.

Abar magnet cut in half will form a total ofpoles.a)fourb)eightc)two

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?

What causes an electric current in a wire?