Bicycling on the Moon: Gravity's Effects on Bicycle Stability

[DaveC426913]

Don't get all mad, Dave. :)

You must have driven your parents crazy in your 'but why is the sky blue?' phase...

 

[Danger]

Don't get all mad, Dave. :)

Dave doesn't get mad; he gets logical. That's far more frightening. I can certainly understand his frustration in this instance. People are trying to counter his knowledge of physics with preconceived notions of how things work based upon terrestrial existence. That irritates me, as well.

 

[ernestpworrel]

You must have driven your parents crazy in your 'but why is the sky blue?' phase...

So you understand where I'm coming from now, do you?

 

[DaveC426913]

So you understand where I'm coming from now, do you?

Uh well, since you ask, I think you've been obtuse, missing the point. Now you seem to be pretending that you were agreeing with me all along.

 

[ernestpworrel]

Now you seem to be pretending that you were agreeing with me all along.

I'd be interested to know why you think this. PM me about it. I think the OP has been answered.

 

[Danger]

It seems kind of obvious from an external perspective. You were arguing against Dave until you realized that you were losing, then turned around and claimed that you were agreeing with him. It might be a clever approach to winning arguments where you come from, but it's way too transparent to fly here.

 

[YellowTaxi]

One thing that hasn't been mentioned is tyre grip on the Moon.

It works out that at 1/6 of Eath's gravity (which is what you have on the Moon) the rubber tyre grip goes down to 1/4 of what it would be here on Earth. (not 1/6, because the coefficient of friction goes up by a factor of about 1.43 for a 1/6 load)

So if a bike on Earth can corner at 1G (9.81m/s/s), on the moon the same bike has max cornering grip of only 1/4G.

So in that sense it would be harder to stay on it. - You'd have to corner a lot slower to keep the bike from falling away from underneath you anyway.

Oh, and braking. You wouldn't be able to stop as quickly for the same reason. Or accelerate - bikes accelerate pretty fast from a standstill here on Earth, so just getting going could be quite difficult - though I admit I've never tried this myself..

 

[Danger]

But we'd be using Moon rubber; surely that's different...

 

[Bob S]

One thing that hasn't been mentioned is tyre grip on the Moon.

It works out that at 1/6 of Eath's gravity (which is what you have on the Moon) the rubber tyre grip goes down to 1/4 of what it would be here on Earth. (not 1/6, because the coefficient of friction goes up by a factor of about 1.43 for a 1/6 load..

The coefficient of friction (COF) is a unitless ratio of the horizontal force to push (or pull) an object divided by its (vertical) weight (gravitational force mg) on the moon. Why does the COF change on the Moon?
Bob S

 

[YellowTaxi]

The coef of friction for rubber goes up if the force pushing it down is lower.

i.e. It just happens that for rubber the coef of friction isn't at all constant, and rubber grips a little better with less weight on it. That's why race cars are usually built as light as regulations allow, to give them max grip.

Moving to the Moon makes things a bit weirder, because you're not reducing the mass of the vehicle, only it's weight is reduced. It's the weight (or normal reaction to the weight if you prefer) that gives the tyre it's grip. The mass is that which tries to keep the vehicle moving in a straight line. That has stayed the same as on Earth, but your friction is less.

I think I explained that a bit backwards, I probably should have put the 3rd paragraph first to explain why grip is lower on the moon in the first place. The fact the coef of friction changes a bit adds some extra info but isn't that important is it. As far as I know the info I've given is correct.

 

[DaveC426913]

I'd be interested to know why you think this. PM me about it.

I don't really see how any good can come from that.