* The momentum before the collision equals the momentum after the collision.
Here's why:
* Momentum is a vector quantity: It has both magnitude (amount) and direction.
* In a closed system: No external forces act on the system.
* Conservation of Momentum: In the absence of external forces, the total momentum of a system remains constant.
Here's what happens in detail:
1. Before the collision: Each object has its own momentum (mass * velocity).
2. During the collision: The objects exert forces on each other, causing a change in their individual momenta.
3. After the collision: The objects are now stuck together, moving as a single unit. Their combined momentum is the vector sum of their initial individual momenta.
Since momentum is conserved, the combined momentum after the collision is equal to the sum of the initial momenta of the two objects.
Example:
Imagine a car (A) of mass 1000 kg moving at 20 m/s collides head-on with a stationary car (B) of mass 500 kg.
* Before the collision:
* Momentum of car A = 1000 kg * 20 m/s = 20000 kg m/s
* Momentum of car B = 0 (since it's stationary)
* After the collision:
* The two cars stick together, forming a combined mass of 1500 kg.
* To conserve momentum, the combined velocity of the two cars after the collision will be 13.33 m/s (20000 kg m/s / 1500 kg).
Key takeaway: Even though the individual momenta of the objects change during the collision, the total momentum of the system remains constant.
