What is thought to make the earth behave as if it contained a huge bar magnet?

If an athlete runs once around a track, back to the starting line, her average velocity is zero. true or false?

While carrying a heavy box up the stairs,you set the box on a step and rest. then you pick up the box and carry it to the top of the stairs. describe these actions in terms of balanced and unbalanced forces acting on the box.

When a metal and an bond they do not share electrons