Newton’s third law: the law of action and reaction
Newton’s third law states that:
- when two bodies interact, they apply forces to one another that are equal in magnitude and opposite in direction.
- This law is important in analyzing problems of static equilibrium, where all forces are balanced, but it also applies to bodies in uniform or accelerated motion.
Example:
A book resting on a table applies a downward force equal to its weight on the table.
- According to the third law, the table applies an equal and opposite force to the book.
- This force occurs because the weight of the book causes the table to deform slightly so that it pushes back on the book like a coiled spring.
