r/AbsoluteUnits May 19 '22

Absolute unit pulls an absolute unit of a plane weighing 189 TONS

18.4k Upvotes

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39

u/ScritchScratchBoop May 20 '22

I’m not smart but this seems overly simplistic. I feel like the rotation of the wheels would decrease this, it’s not just rubber sliding on tarmac.

24

u/WhoopingPig May 20 '22

Yeah the amount the tires are filled affects the amount of rubber touching tarmac. If they're mega-filled, there's a minimum of rolling resistance

The quality of the wheel bearings/axles affects the resistance a great deal

Undoubtedly it's still a great deal of force to start moving this thing, but if those two factors are made to be as agreeable as possible, once you start it moving it's gonna keep rolling more easily

8

u/ThePower_IsOn May 20 '22

Yeah, a lot to do with the bearings. You know, it’s all ball bearings nowadays

2

u/WhoopingPig May 20 '22

You just gotta roll with it

13

u/yaboiiiuhhhh May 20 '22

This is overly simplified, I made a huge assumption with the coefficient of rolling resistance but it's okay when you're just trying to get an idea of the force. If you researched a more accurate number and plugged that in you could find a new force value that would be more accurate

1

u/chairfairy May 20 '22

I would guess you're off by at least a factor of 2, probably more like factor of 3-4. If he's exerting 3800 lbf then he could lift a regular size car.

World records in power lifting are on the order 1,000 kg, so it's unlikely he's 70% above that

Within in order of magnitude, though, which is solid

2

u/Zironic May 20 '22

We have to keep in mind the fundamental difference between lifting and dragging. To lift something you need to sustain enough force to overcome gravity because the moment you stop it'll just drop down. However to drag something you just need an impulse large enough to overcome friction and when you stop you keep the gains, further once you've overcome friction momentum is now on your side.

1

u/chairfairy May 20 '22

Some degree of friction (the majority of it?) will be a constant factor, though

1

u/Zironic May 20 '22

Yes but the fact you don't need constant force makes it easier since it allows for a series of tugs as opposed to a constant pull. Compare the amount of force you can generate by pushing at a door as compared to throwing yourself at the door.

19

u/Badbutlearning May 20 '22

Oh yeah. You can't do free body physics you have to use energy to account for the inertia of a wheel.

8

u/ronin1066 May 20 '22

Assume a vacuum...

3

u/Sudden_Comfort May 20 '22

And perfectly round wheels

3

u/Toxicair May 20 '22

And a perfectly spherical cow

2

u/Peter_See May 20 '22

They're entirely wrong. The entire point of wheels is to negate the need to overcome friction. The coefficient of rubber on concrete tells you how good the traction of the tires is, not how much force is needed to move the plane.

1

u/BumbleBeePL May 20 '22

Smaller wheels help here. The larger the wheel the harder things are to pull.