Sorry. I cannot accept your explanation. You eliminate the possibility of using centripetal force as being part of your work output equation by framing your equation in that manner. If you "a priori" exclude centripetal force, then obviously it seems that centripetal force doesn't require energy to become operant. The energy may not be utilised to generate forward momentum (forward kinetic energy) along the race track (in the car example), but energy is required to keep the car on a circular track (and the car's tires know that).
I'm sorry you're sorry you cannot accept my explanation but I assure you it is the one and only technically correct one. First off the force is called tension (axial load)... and it has two components (one in the normal, perpendicular to path i.e. centripetal direction and one in the tangential direction.) The normal component of the tension force does not move the object closer to the center of rotation and therefore it does NO WORK! The tangential component on the other hand accelerated the object along the path. The tangential component (and this is the one thing BerntR and I can agree on) is what does the work.
Originally Posted by Jeff
Consider a simple example.
Imagine traveling in a NYC subway car that is traveling at 40mph on a straight rail track. Imagine that you are standing in the center aisle and holding onto a vertical post. Then imagine what happens when the subway car goes around a tight bend at the same speed. You will have to hang onto that vertical post for "dear life" to prevent yourself from being catapulted down the length of the subway car. It requires "energy" to remain stationary in balance and that energy is the energy required to offset a centrifugal force acting on your body. I would imagine that the subway car also needs to expend energy to stay in balance on its circular track, and that energy is centripetal energy.
Jeff.
NO it does not require energy! It requires a FORCE (see click here->Centripetal force requirement. This is why we have a variety of words in the lexicon: FORCE WORK ENERGY etc. soforth.... They have different meanings. AGAIN.... SOME FORCES DO NO WORK.
If you are hanging motionless on a jungle gym there is a force in your arms .... but you're not doing work... you're not expending power... You're hanging there motionless. You don't do work until you do a pull up. When you do a pull-up you are moving that force (mass X gravity) through a distance ... THAT is work... THE requires Hp. Hanging Motionless does not..... but there is a FORCE present when you hang motionless... make no mistake about that!
I'm done with this one.... believe what you want to.... makes no difference to me really.... Merry Christmas Jeff
You state-: "'m sorry you're sorry you cannot accept my explanation but I assure you it is the one and only technically correct one. First off the force is called tension (axial load)... and it has two components (one in the normal, perpendicular to path i.e. centripetal direction and one in the tangential direction.) The normal component of the tension force does not move the object closer to the center of rotation and therefore it does NO WORK! The tangential component on the other hand accelerated the object along the path. The tangential component (and this is the one thing BerntR and I can agree on) is what does the work."
You write that tension force has two components - a tangential component and a centripetal component. You then state that only the tangential component does work, because it propels the object along a a path. However, if the path is circular (rather than a straight path), then some other "force" must be doing work to make the object move along a circular path rather than a straight line path. In other words, that other "force" is doing "work" to centripetally accelerate the object (centripetal force is defined in Wikipedia as the force needed to move an object along a circular path rather than a straight path).
You write-: "The normal component of the tension force does not move the object closer to the center of rotation and therefore it does NO WORK! "
That statement makes no sense to me - if a moving object moves from a straight line path to a circular path, then it is moving closer to the center of rotation.
nm golfer
...snip
That statement makes no sense to me - if a moving object moves from a straight line path to a circular path, then it is moving closer to the center of rotation.
Merry Christmas to you!
Jeff.
Quote:
"It took Newton to show us that the Moon is falling to Earth"
By definition there is no point on a circle that is closer to the center of the circle than any other....... I'll leave it at that.
nmgolfer - you wrote-: "there is no point on a circle that is closer to the center of the circle than any other."
That is correct. Imagine that there a million points on that hypothetical circle's circumference, and imagine that an orbiting object (traveling at a constant finite speed) has to move from from one point on the circumference to the next point on the circumference to the next point on the circumference -- and that it has to complete this process one million times to complete one orbit. In each of those movements (from one point to the next point), the orbiting object needs a tangential force to move it at its constant "finite" speed and a centripetal force to keep it moving on the circular path.
After penning post #265, I have come back to this post to add another comment.
My final statement above was "a centripetal force to keep it moving on a circular path." Keeping an orbiting object traveling in a circle requires a restraining force, a force that prevents the orbiting object from moving off into space (in a straight line direction at right angles to the circumference of the circle). That restraining force, which keeps the orbiting object traveling along a circular path, represents centripetal force, and the constant use of a restraining force (centripetal force) requires the constant expenditure of energy - and that represents work.
Jeff.
Last edited by Jeff : 12-24-2008 at 08:10 PM.
Reason: add final commentary
You wrote regarding centrieptal force-: "NO it does not require energy! It requires a FORCE (see click here->Centripetal force requirement. Thi s is why we have a variety of words in the lexicon: FORCE WORK ENERGY etc. soforth.... They have different meanings. AGAIN.... SOME FORCES DO NO WORK."
That's nonsense. If a force is operant, then it must be using energy and therefore doing work.
You equate work only with displacement of an object in space. You do not consider it work to keep an object stationary in the face of opposing forces. However, it does require energy to keep an object stationary if there is another force acting to displace that object. For example, if person A is pushing a three foot X three foot diameter block of steel on an ice rink, then it requires energy to move the block against the resistance of the ice. If person B then stands opposite the block and pushes in the opposite direction with the same degree of force as person A is exerting to push it forward, then person B is using energy, and person B is doing work, even though the block of steel is now stationary (not moving, not being displaced).
Therefore, in your example of a person hanging from a jungle gym by his arms, he is doing work even though he is stationary. He is constantly using muscle energy (doing muscle work) to overcome the effect of gravity on his body mass. If he didn't constantly perform that muscular work, gravity would pull his body down to the ground. You wrongly believe that he is only working when he he does chin-ups and pulls his body up.
You sent me to the following website, which demonstrates that a centripetal force must be using energy, and the constant expenditure of energy represents work.
In that first animation, the ball travels in a straight line if there is no force (requiring energy expenditure) to keep it stationary. In the second animation, a block provides a force that keeps the ball stationary - and that represents centripetal force. Any force that is constantly operant requires energy and therefore centripetal force must be performing work. In other words, energy is required to keep the ball stationary (from traveling forward in a straight line) and the restraining force that provides the "energy for restraint" is performing work.
Hopefully, you are wise enough to realise that your car seat belts (or car airbag) will be performing work to keep you from being ejected through the windscreen if you hit another car head-on at 100mph. The work it is performing is to prevent you from becoming an instantaneous human projectile!
I suspect that you don't spend much time studying golf swings using a swing analyser program and that you don't plot the clubhead arc and hand arc to see what is really happening.
Yeah, and I'm sure you never looked at an x-ray during your residency.
I've only given about 13,000 video lessons in the last ten years. I hope I can learn how to use the software before I start getting really busy.
No offense but.... before you go any further in your study of the golf swing you really need to STOP! and go take a high school level physics class. I'm dead serious.
What you are saying is absolutely laughable. ITS COMPLETELY AND TOTALLY RIDICULOUS. I would be laughing if I weren't crying. No wonder GOLF myths have perpetuated for so long and are so deeply ingrained.
Try the community college or take the online course at the link I've provided BUT DO IT! You need a basic understanding of these really simple physics principles or else you are wasting EVERYONES' (but especially your) time. Its like someone trying to operate having never studied anatomy. Show my profession some respect!
I will not discuss this or any other subject with you any further. I've provided ample evidence and plethora of links that SHOULD DRIVE THESE VERY BASIC PHYSICS REALITIES HOME to you. But no... You either won't read them or don't believe them so what gives? If you can't find the time to learn the basics then STOP ANYWAY... Just a suggestion.
You wrote regarding centrieptal force-: "NO it does not require energy! It requires a FORCE (see click here->Centripetal force requirement. Thi s is why we have a variety of words in the lexicon: FORCE WORK ENERGY etc. soforth.... They have different meanings. AGAIN.... SOME FORCES DO NO WORK."
That's nonsense. If a force is operant, then it must be using energy and therefore doing work.
You equate work only with displacement of an object in space. You do not consider it work to keep an object stationary in the face of opposing forces. However, it does require energy to keep an object stationary if there is another force acting to displace that object. For example, if person A is pushing a three foot X three foot diameter block of steel on an ice rink, then it requires energy to move the block against the resistance of the ice. If person B then stands opposite the block and pushes in the opposite direction with the same degree of force as person A is exerting to push it forward, then person B is using energy, and person B is doing work, even though the block of steel is now stationary (not moving, not being displaced).
Therefore, in your example of a person hanging from a jungle gym by his arms, he is doing work even though he is stationary. He is constantly using muscle energy (doing muscle work) to overcome the effect of gravity on his body mass. If he didn't constantly perform that muscular work, gravity would pull his body down to the ground. You wrongly believe that he is only working when he he does chin-ups and pulls his body up.
You sent me to the following website, which demonstrates that a centripetal force must be using energy, and the constant expenditure of energy represents work.
In that first animation, the ball travels in a straight line if there is no force (requiring energy expenditure) to keep it stationary. In the second animation, a block provides a force that keeps the ball stationary - and that represents centripetal force. Any force that is constantly operant requires energy and therefore centripetal force must be performing work. In other words, energy is required to keep the ball stationary (from traveling forward in a straight line) and the restraining force that provides the "energy for restraint" is performing work.
Hopefully, you are wise enough to realise that your car seat belts (or car airbag) will be performing work to keep you from being ejected through the windscreen if you hit another car head-on at 100mph. The work it is performing is to prevent you from becoming an instantaneous human projectile!
Jeff.
Last edited by no_mind_golfer : 12-24-2008 at 11:54 PM.
You wrote-: "What you are saying is absolutely laughable. ITS COMPLETELY AND TOTALLY RIDICULOUS. I would be laughing if I weren't crying. No wonder GOLF myths have perpetuated for so long and are so deeply ingrained."
Whenever I read statements like this, then I know that the person is not dealing with the "issues", but taking an escapist route to avoid dealing with the "issues". You have not provided any proof that my opinions re: work or centripetal force are invalid. You have not even provided a counterargument.
As a physicist, you think that work is only performed when an object moves in space.
Example 1
So, if a person leans against a 6 foot diameter redwood tree and pushes against the tree with all his strength in an attempt to move the tree, you state that the person is not doing any work because the tree doesn't move. If after 15 minutes of continuous pushing, the person falls to the ground in a state of total exhaustion, you are presumably stupefied because he didn't do any work. You apparently fail to understand that muscular energy was used to push against the tree, and that the use of muscular energy represents work - from the person's perspective. It may not be useful work, but energy was expended and the person therefore worked. The amount of muscular work performed by the person pushing against the tree could theoretically be computed by an exercist physiologist - even though you have already concluded that the person didn't do any work because the tree didn't move.
Example 2
Now, if that same person leaned against a 1" diameter sapling tree, and the sapling tree bent-over horizontal to the ground, you would conclude that the person performed work - because he moved the vertical tree through a 90 degree angle. In your mental framework as a physicist, he performed much more work in this second example because he moved the tree - while in the first example he didn't perform any work because the tree didn't move.
OK. We see the world differently.
What really puzzles me is that you believe that it takes no energy (requires no work) to restrain an object been pushed by a force. So, consider the situation of a mother riding in a roller coaster while holding her 4 year child in her arms, and imagine that the mother is restrained with seat belts while her child is only restrained by the mother's hold with her arms. Then imagine the roller coaster going through a tight bend at 100mph. The mother has two choices. She could refuse to expend any energy by deliberately holding onto her child with her arms, and the consequence of that decision would be a child being propelled into space with an amazing amount of projectile force when the roller coaster enters the tight bend at 100mph. Alternatively, the mother could use all of her arm strength to hold the child tightly against her body to prevent the child from being ejected from the roller coaster. In my world, the mother used an enormous amount of energy to perform that holding action, and that represents work. In effect, I would say that the mother was performing the work of a centripetal action - the action of ensuring that her child continued moving at 100mph on a circular path rather than a straight line path. In your world, the mother was not performing any work because she didn't use tangential forces to move the child (having a certain quantifiable mass) a certain distance.
BerntR
Energy doesn't get banked (stored ... dollars in an account) ... the downswing converts potential energy to kinetic. Forces across levers create movement.... that's kinetic energy.
Oh really ......
Energy storage is a very essential topic in a lot of mechanical engineering subjects like noise control and vibration damping. Transducer technology is a subject I know pretty well where energy storage is an essensial challenge. In many cases the efforts are about minimizing energy storage. In other cases it's about tuning. Typical efforts to reduce energy storage in mechanical systems is to reduce mass and add mechanical resistance.
Energy storage is often described with a Q-factor that deals with the ratio of reactive (energy-storing) components to resistive (energy-dissipating) components. http://en.wikipedia.org/wiki/Quality_factor
The down swing converts potential energy (related to g) to kinetic energy, that's true. In addition it stores the kinetic energy that is added by the player working the club. Moving mass is one of the essential ingredients. Most of the mass in the clubhead is there to help the player accumulate energy until impact.
Linear Mode
