The force that opposes the motion of objects as they touch and pass is friction.

Here's a breakdown:

* Friction is a force that resists the relative motion of two surfaces in contact.

* It arises from the microscopic irregularities and interactions between the surfaces.

* It always acts in the opposite direction of motion.

There are two main types of friction:

* Static friction: This acts on objects at rest, preventing them from moving.

* Kinetic friction: This acts on objects in motion, slowing them down.

So, when objects touch and pass, the force of friction opposes their movement, causing them to slow down.