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Re: [Phys-l] Centrifugal redux



But if the forces are balanced I should be going in a straight line at constant speed.

I'm turning because I have a horizontal component of lift perpendicular to my motion.

Sorry - I am not a convert to the idea of "centrifugal force". I prefer to trust my attitude indicator to tell me that I am banked and my heading indicator to tell me I'm turning - believing in the "forces" I feel will have me ending up like John F. Kennedy Jr.

Bob at PC

________________________________

From: phys-l-bounces@carnot.physics.buffalo.edu on behalf of John Denker
Sent: Tue 3/17/2009 5:48 PM
To: Forum for Physics Educators
Subject: Re: [Phys-l] Centrifugal redux



On 03/17/2009 11:56 AM, LaMontagne, Bob wrote:
When I was getting my sailplane license I remember having to learn in
ground school that the inward component of lift when going in a circle
is just balanced by the centrifugal force.

So far so good.

My question as to why you
would then fly in a circle was not welcomed by the instructor.

Answer: You're flying in a circle by hypothesis. That is,
it's a premise of the scenario. If you weren't flying in
a circle there wouldn't be any centrifugal field.

The principle is simple: The centrifugal field exists if and
only if you are using a rotating reference frame.

This is covered in the text starting at
http://www.av8n.com/how/htm/motion.html#sec-rotation-intro

John S. Denker
Advanced and Instrument Ground Instructor

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