The quantity of motion of a moving body, measured as a product of its mass and velocity.

Momentum:
Momentum is a fundamental concept in physics that describes the motion of an object. It is defined as the product of an object's mass and its velocity. The momentum of an object can be calculated using the formula:

Momentum (p) = mass (m) × velocity (v)

Newton's Third Law of Motion:
Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. This means that when two objects interact, the forces they exert on each other are equal in magnitude but opposite in direction. This law can be summarized as follows:

"For every action, there is an equal and opposite reaction."

Explanation:
Momentum:
Momentum is a vector quantity, which means it has both magnitude and direction. The magnitude of momentum depends on the mass and velocity of an object. The greater the mass or the faster the velocity, the greater the momentum.

Newton's Third Law of Motion:
Newton's Third Law of Motion explains how forces act in pairs. When an object exerts a force on another object, the second object exerts an equal and opposite force on the first object. These forces are called action and reaction forces.

Example:
For example, consider a football being kicked. When the player kicks the ball, they apply a force to it. According to Newton's Third Law, the ball exerts an equal and opposite force back on the player's foot. This is why the player feels the impact of the kick.

Implications:
Newton's Third Law has several important implications. It explains how objects interact with each other and how forces are created. It also helps explain phenomena such as the recoil of a gun when fired or the propulsion of a rocket.

Conclusion:
In conclusion, momentum is the product of an object's mass and velocity, while Newton's Third Law of Motion states that for every action, there is an equal and opposite reaction. These concepts are fundamental in understanding the motion and interactions of objects in physics.