Momentum conservation is an important idea to understand when looking at how objects collide. However, it can be a bit tricky. Here are some of the main challenges we face:

1. Understanding Different Types of Collisions:
   It can be hard to tell the difference between elastic and inelastic collisions.
   In elastic collisions, both momentum and kinetic energy stay the same.
   But in inelastic collisions, only momentum is conserved.

2. Using Math:
   To use the conservation of momentum, we need to work with several equations.
   We also need to know about direction, which adds to the difficulty.
   When collisions happen in two directions, the math can get very complicated.
   We have to use the formula $p_{initial} = p_{final}$ for each part of momentum.

3. Real-life Complications:
   Things like friction and bending can change how collisions work in real life.
   This makes it hard to guess what will happen when objects collide.

Even with these challenges, you can improve your understanding.
Practice using problem-solving strategies that involve breaking down momentum into parts.
By applying the conservation laws step by step, you can get a much better grasp of the topic!