There's no force that specifically *maintains* motion. It's a bit of a tricky concept because it's actually the *absence* of a force that allows motion to continue. Here's why:

* Newton's First Law of Motion (Inertia): An object at rest stays at rest, and an object in motion stays in motion at a constant velocity (same speed and direction) *unless acted upon by a net force*.

* Forces Cause Changes: Forces are "push" or "pull" that can change an object's velocity (speed or direction). So, the absence of forces means no changes in velocity.

Think of it like this:

Imagine a hockey puck gliding across the ice. If there was no friction, the puck would continue to move at a constant speed in a straight line forever. It's not that a force is keeping it moving, it's that there are no forces acting on it to *stop* it.

Here's where it gets interesting:

* Friction: In the real world, we always have forces like friction (between the puck and ice) that slow things down.

* Gravity: Gravity also acts on objects, even when they're moving. If you throw a ball up in the air, gravity acts on it, slowing it down and eventually pulling it back down.

So, the key takeaway is:

* Motion isn't maintained by a specific force.

* It's the *absence* of forces that allows objects to continue moving at a constant velocity.

* Forces are what cause changes in motion.