Walter....
This makes good sense to me. Thanks, again.
Gordy
From: WALTER/SUE SIMBIRSKI <simbirsw@xxxxxxx>
To: Gordon Hill <hillshead@xxxxxxx>
Subject: Re: acceleration / deceleration
Date: Mon, 30 Oct 2006 14:01:57 -0700
Gordy - deceleration is just negative acceleration. In the case of the spinning propellor we are dealing with two forms of acceleration - linear acceleration, which exists because the propellor tip is always changing direction - and angular acceleration, which is defined by the amount of angular momentum of the propellor.
If we look at a a spinning top it will stay upright if it has enough angular momentum. If it keeps spinning at the same rate (in degrees per second) it will continue to remain upright because the angular momentum remains constant (there is no angular acceleration or deceleration taking place). As it slows down (it experiences negative angular acceleration, i.e. angular deceleration) it loses momentum and eventually falls over.
As the propellor slows down there is a linear deceleration because the rate of change direction of the point on the blade tip slows down and there is angular deceleration because angular momentum is also decreasing.
As you can see the angular and linear acceleration for a spinning object are related in that if angular acceleration is increasing then linear acceleration will also increase, when angular acceleration is zero then the linear acceleration is constant, and when angular acceleration is decreasing then the linear acceleration is also decreasing.
I will definitely include definitions for speed, velocity, acceleration and deceleration as they apply to linear and angular movement. I also think force/load/torque, energy/work, momentum, friction, mass, weight and frame of reference should be included.
My intent is to keep it at the level where the mathematics is confined to add, subtract, multiply and divide. This should be enough for most people.
Walter
From: Gordon Hill <hillshead@xxxxxxx>
To: simbirsw@xxxxxxx
Subject: acceleration / deceleration
Date: Mon, 30 Oct 2006 14:52:24 -0500
Walter...I assume that when you write the article, you will consider adding definitions for SPEED, VELOCITY and ACCELERATION.
What about DECELERATION ?
If that propeller does not spin at a constant speed, but does so more and more slowly, is that not, "DECELERATION " ?
Yet we still have velocity which is constantly changing direction .(????)
Gordy