### Short Answer

## 7.2 Newton's Law of Universal Gravitation and Einstein's Theory of General Relativity

Newton’s third law of motion says that, for every action force, there is a reaction force equal in magnitude but that acts in the opposite direction. Apply this law to gravitational forces acting between the Washington Monument and Earth.

- The monument is attracted to Earth with a force equal to its weight, and Earth is attracted to the monument with a force equal to Earth’s weight. The situation can be represented with two force vectors of unequal magnitude and pointing in the same direction.
- The monument is attracted to Earth with a force equal to its weight, and Earth is attracted to the monument with a force equal to Earth’s weight. The situation can be represented with two force vectors of unequal magnitude but pointing in opposite directions.
- The monument is attracted to Earth with a force equal to its weight, and Earth is attracted to the monument with an equal force. The situation can be represented with two force vectors of equal magnitude and pointing in the same direction.
- The monument is attracted to Earth with a force equal to its weight, and Earth is attracted to the monument with an equal force. The situation can be represented with two force vectors of equal magnitude but pointing in opposite directions.

True or false—Gravitational force is the attraction of the mass of one object to the mass of another. Light, either as a particle or a wave, has no rest mass. Despite this fact gravity bends a beam of light.

- True
- False