A loaded tractor-trailer has a mass of 36,000 kg, what is it's weight?

That depends on WHERE the rig is, because

weight = (mass) x (acceleration of gravity where the object is).

- - If the truck is on Mars, then

Weight = (36,000 kg) x (3.71² m/s²) = 133,560N.

- - If the truck is on the moon, then

Weight = (36,000 kg) x (1.62 m/s²) = 58,320N.

- - If the truck is on Earth, then

Weight = (36,000 kg) x (9.81 m/s²) = 353,160N.

It all depends.