[Phys-L] Re: getting tired

[Bernard Cleyet <bernardcleyet@REDSHIFT.COM>]

Don't need to assume equality;   assume contact force is normal.

It's the difference in pressure that holds up the bike.

Here's a "thought" soln.:   With no air, the rim and tire rubber hold it
up (gauge p=zero), as one adds air, the bike lifts; more air less
contact area (once it's riding on air and not rim)

bc, prays he's got it.

Anthony Lapinski wrote:

> Suppose you know the pressure inside your bike tires and the contact area
> between each tire and the ground. Assuming the bike is supported equally
> by the two tires, you can determine the weight of the bike.
>
> Here's my question. In using the formula for pressure (P = F/A), do you
> use the GAUGE or ABSOLUTE pressure in the tire for this calculation (Pgau
> = Pabs - Patm)? I'm thinking gauge since the atmosphere is pushing from
> the outside on ALL parts of the bike. And this give rise to a buoyant
> force on the bike? Can anyone assist me through this subtle distinction as
> it relates to the bike problem?
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