On 29/7/2007 5:42 PM, Horace Heffner wrote: > > On Jul 29, 2007, at 1:44 PM, Harry Veeder wrote: > >> >> I know enough about the subject to admit error when I have not >> made adequate use of Newton's laws of motion. > > My statement is not aimed at admission of error if or when error is > made. It is about a method to help you discover and understand > principles for yourself, one that I use myself. I find it amazing > the number of times I start out writing a post only to discover it is > completely wrong.
The creative process is never really wrong. > I think it is often the act of writing, of > struggling for clarity of expression and for clear justification > based on known principles, that leads to discovery. In the words of > David Melton, "The best ideas come from the work, not from our > heads." He was referring to writing in general, but I think it goes > double for physics. We all have our own ways of working. I like what Karl Popper says "I may be wrong and you may be right, and by an effort, we may get nearer to the truth." > > >> >> Do you think the above prediction is not allowed by Newton's laws? > > It is clear from your discussion that you don't understand angular > momentum, angular velocity, moments of inertia, and their relations. > An object in motion remains in motion unless acted upon by a force. > This goes for angular motion as well as linear motion. If you > suggest an object will change its angular (rotational) velocity then > it is essential to identify the source of the torque (angular force) > which does this. Things don't arbitrarily change their angular > velocity without a torque. My thought experiment does not show angular velocity _changing_. I hope it shows how two systems which ought to posses the same angular velocities actually posses _different_ angular velocities. If don't like the difference and wish to make it vanish by invoking this or that principle then go ahead. > There is no principle that states things > tend to seek a zero angular velocity with respect to the fixed stars > for example. Where did I say that? (Perhaps we do need such principle...but i'm just thinking freely) > Radial force won't change angular velocity either. Only > tangential force, which is known as torque. If you apply torque to an > object its angular velocity will change. There is only so much > energy you can get out of an object by breaking it using the moment > of inertia of another object. Soon they both rotate at the same > speed. The torque is equal and opposite to the opposed torque. > > Again, I think of you try to write your predictions with full > justification and explanation for each step, using terms of angular > acceleration, angular velocity, torque, and moment of inertia, then > it may help you understand the principles. These terms are all > analogous to similar terms with regard to linear momentum, described > by Newton's laws, and the principles can be derived from Newton's > laws. We are not performing brain surgery or building rockets. No one is going to be sued for a misjudgement or a mistake. > Here are the correspondences: > > acceleration: angular acceleration, > velocity: angular velocity, > force: torque: and > inertial mass: moment of inertia I know what these things are. > If you think an angular velocity machine can produce free energy just > convert it into a linear machine to see why it won't work. My question was not about free energy. Harry
