yes the sizes of skateboard wheels range from 40-70 mm
Yes, they are called Avic
Wheels dont make a skateboard easier to turn on the skateboard trucks do that.
because you are determining whether distance is affected by the wheels, wheels would thus be the manipulated variable. I recommend using different wheel sizes or eeven hardness, but your best bet would be to test size.
The wheels allow them to move. If you look at a skateboard it has wheels.
Skateboard companies make decks and wheels
There are no trunks on a skateboard, you are probably referring to the "trucks" which are the parts the wheels attatch to.