I have a question for you. As I was driving to work this morning, I passed a big rig and it got me wondering how much effort it would take something like my GMC Envoy to move an empty semi trailer on a flat surface. That got me wondering about the physics of pulling something on wheels as opposed to pulling something without wheels.

How does one determine the effort needed to pull something on wheels vs. something not on wheels?

If an empty semi trailer weighs 15,000lbs, on a flat surface it should feel like pulling less because the wheels mitigate some of the friction, right?