In a perfectly inelastic collision, two objects crash into each other and stick together. After the crash, they move as one. Here are the main points to know:

1. Momentum Conservation:

   • The total momentum before the collision is equal to the total momentum after the collision. You can think of momentum as the “motion power” of an object. We can say:

   Total momentum before = Total momentum after

2. Kinetic Energy Changes:

   • Kinetic energy, which is the energy of moving things, doesn’t stay the same. Before the crash, the total kinetic energy is more than it is after the crash.

Here’s an example to make it clearer:

Let’s say we have two objects. They each have different weights. We call them $m_1$ and $m_2$. Before the crash, they are moving at different speeds, which we call $v_1$ and $v_2$. After they crash and stick together, their final speed ($v_f$) can be found using this formula:

Final speed = (Weight of object 1 × Speed of object 1 + Weight of object 2 × Speed of object 2) ÷ (Total Weight of both objects)

This situation shows how kinetic energy can change into other forms, like heat and sound, when the objects crash together.