# A wheel's spin rate to land speed: HOW to calculate?

• I know nothing about mathematics. That's not about to change... I'm a visual thinker... which means I draw. With crayons. And food.

If a wheel is not touching the ground, but is spinning, and the rate of spin is known, and its diameter is also known, is it possible to calculate what speed that wheel would be moving if it were to be in contact with the ground at that rate of spin?

If so, how?

Yes, I know... if you know maths this isn't rocket science. For me it is.

• Speed (metres per second) = diameter × π × rate of spin (in revolutions per second)

Speed (metres per second) = diameter × π × rate of spin (in degrees per second) ÷ 360

π (The maths circle thingy called Pi) = 3.14159265359... bla bla bla goes on forever, but that should be more than enough decimals to get it very accurate.

• @Aidan-Oxley Is the Get and Set Velocity of hyperPad Physics Behaviours using metres per second? Or some other arbitrary number/scale/system?

• @Aidan-Oxley And... THANK YOU!!!
Looks so simple... like this. But my mind still torqued.

• @Deeeds Get and set velocity are metres per second. If you look at the behaviour somewhere it should say m/s which means metres per second.

• @Aidan-Oxley argh, of course... it's only when you start using it you get to see more about it. Typical programmer explanations in the "information" section. Just enough to begin to get confusingly worded, at which point the documentarian has given up and moved on.

• @Deeeds Rotational velocity in hyperPad is in revs per minute, so you need a new formula:

Speed (metres per second) = diameter × π × rotational velocity (revs per min) ÷ 60

Less behaviours version:
Speed (metres per second) = diameter × rotational velocity (revs per min) × 0.05235987756

• @Aidan-Oxley Yeah, got this. This unit of measure was actually mentioned in the "docs"... and /60 is one of the few math-like things I can do. Cheers.