1. Friction: This is a force that opposes motion between two surfaces in contact. It can be caused by the roughness of the surfaces or the presence of a fluid between them. Friction acts in the opposite direction of motion and reduces the momentum of an object.

2. Air Resistance (Drag): This force acts on objects moving through the air. It is caused by the collision of air molecules with the object's surface. Drag force increases with the speed of the object and the size of its surface area. Like friction, it acts opposite to the direction of motion and slows down the object, decreasing its momentum.

These are just two examples, and many other forces can hinder momentum. For example, gravity can also significantly impact an object's momentum by pulling it downwards.