A bungee jumper with a weight of 613 N leaps off a bridge. He is in free fall for a distance of
22.6 m before the cord begins to stretch. How
much work, in kilojoules, does the force of gravity
do on the jumper before the cord begins to
stretch?

Phase changes are chemical changes. true or false

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?

The two stars in a certain binary star system move in circular orbits. the first star, alpha, has an orbital speed of 36 km/s. the second star, beta, has an orbital speed of 12 km/s. the orbital period is 137 d. a) what is the mass of the star alpha? b) what is the mass of the star beta?