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Re: A Friday Physics Problem

To: "Jay Mitchell" <jemitchell@compuserve.com>, autox@autox.team.net
Subject: Re: A Friday Physics Problem
From: dg50@daimlerchrysler.com
Date: Fri, 19 Nov 1999 12:25:40 -0500

Aha! A good answer.



>> In order for Car B to maintain the same
>> speed through the turn as Car A, it must either be capable of
>> maintaining a higher lateral acceleration.

> Nope.

Yeah, I kinda thought that sounded dodgy...

OK, so here's the essentials

Car A: Mass of m, thrust of F
Car B: Mass of 2m, thrust of 2F

as F/m = 2F/2M, both cars accelerate the same in a straight line

But when it comes time to turn a radius r, the force f to maintain the turn at
the (common) velocity v is

mv^2/r for Car A, and
2mv^2/r for Car B

So we conclude that Car B will require twice the grip to maintain the same speed
through the turn.

Now here's where it gets interesting:

If we assume that both cars have the same level of grip (f), then Car B must
slow down to make the turn.

Solving for v, we get

sqrt(rf/m) = v

Meaning that v varies as the square root of one over the mass. (uhh, right?)

Something doesn't seem right with that conclusion, could someone check it?

DG




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