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 (speed and direction) unless acted upon by a net force.

This means:

* No force is required to keep an object moving at a constant velocity. Imagine a puck sliding on a frictionless surface – it would continue moving forever in a straight line without any force acting on it.

* A force is only necessary to change an object's motion:

* To start it moving from rest.

* To speed it up or slow it down.

* To change its direction.

Let me know if you'd like more examples!