Strike #2
nmgolfer has produced 3 posts in this thread. They are as usual very pedantic and arrogant. He wipes my ideas away as having no value, being totally wrong and suggest that my education hasn’t gone beyond kindergarten, etc., etc..
In these three posts filled with this kind of bla bla bla, there is only one substantive argument to support his attack on my ideas. His irritating and childish attitude finally convinced me to have a closer look at this single substantive argument.
Hi There
Sadly I must raise the BS flag once again. This analysis strikes me as wrong... just plain wacky really. Mandrin would have us believe a flexible beam with a mass on the end would contort as shown in figure 3 as the pendulum swings under the influence of gravity. Furthermore he would have us believe this "shaft deflection" results in the mass at the end having 29% more kinetic energy when it reaches the bottom (than the stiff shafted counterpart). I dispute those findings.
Taken to the extreme, it is not hard to imagine a mass at the end of a string. Wouldn't that be the ultimate flexible beam... a nearly massless string? What happens when a mass at the end of a taut string is released from a horizontal position as shown in Mandrins diagram? Does it contort as shown in figure 3a? No it does not contort; the string remains taut. Try this yourself at home.
The mechanics of pendulums (both simple such as mass at the end of a massless string and physical or "real" pendulums having distributed mass) are discussed in every first year physics text. T or period = 2pi(I/k')^.5 Kinetic energy is also well defined (mv^2)/2. Assuming there are no losses (aerodynamic drag or friction at the pivot) the mass at the end of the pendulum will have identical kinetic energy when it reaches vertical regardless whether the its connected to a massless string (i.e. flexible... whippy tempomaster shaft) or a super heavy superstiff steel shaft. v = (2gh)^.5 => E = m g h where h is the height if falls... in otherwords... shaft length. This simple principle is called "conservation of energy".
He maintains (above) with his usual arrogant certitude that the value of the mass m1 of the shaft, connecting the pendulum mass m2 to the pivot, has no influence whatsoever on the kinetic energy, and hence the velocity, of the pendulum mass m2 at the bottom when reaching the vertical postion.
This is his unique substantive argument to deny any validity to my post showing the flexible shaft gaining 29% in velocity, relative to a rigid shaft, using the potential energy due to bending of the shaft.
Well it might come as an unpleasant surprise to nmgolfer but he is totally and completely wrong.
This is the second time that I surprise him with his pants down.
His credibility is really getting down to sub zero levels.
The situation to be anlyzed is shown in the Figures below.
One can readily derive that, for the situation of Fig2, the velocity of m2 at the bottom is, for a release from a horizontal starting position, given by equation (2). It is eminently evident that the magnitude of the mass of
m1 has an influence on the velocity V, and hence kinetic energy of mass m2, clearly contrary to nmgolfer’s assertions.
nmgolfer, it is clearly showing that you have no knowledge of multibody dynamics or dynamics of continuous systems; even the dynamics of particles seems beyond you, seeing the gross errors you are making, maltreating very simply problems regarding pendulums.
BTW, I am not finished with you yet, more to come.… and please..... don’t forget to show this post to your colleagues.
