Momentum is a measure of an object's mass in motion. It's calculated by multiplying mass (m) and velocity (v):
* Momentum (p) = mass (m) x velocity (v)
Key Principles:
* Conservation of Momentum: In a closed system (one with no external forces), the total momentum remains constant. This means the momentum before an event (like a collision) equals the momentum after the event.
* External Forces: These are forces that originate outside the system. They can be applied by objects outside the system or by fields like gravity.
* Internal Forces: These forces act between objects within the system. They cannot change the system's total momentum because they always occur in equal and opposite pairs (Newton's Third Law).
Examples of External Forces that Change Momentum:
* Gravity: The Earth's gravitational pull is an external force acting on objects near its surface. It causes objects to accelerate downwards, changing their momentum.
* Friction: This force opposes motion and arises from contact between surfaces. It can slow down or stop objects, decreasing their momentum.
* Air Resistance: This force opposes the motion of objects through the air, slowing them down and changing their momentum.
* Applied Forces: Any force applied from outside the system (like a push or pull) can change the momentum of objects within the system.
In Summary:
The total momentum of a system remains constant unless acted upon by a net external force. Internal forces within the system do not change the overall momentum.
