John,
It is rather amusing to see the super fast evolution of your posts in just a few days.
First, very, very complimentary indeed, then draping yourself in life time science teaching and invoking buddies form Cambridge University to impress and belittle me, then more ridiculing mandrin and his fairy tales and finally some smart damage control when finally realizing your are completely wrong after all.
In your wake you got for sure this Bronco Billy individual, smelling blood, losing control and hence ridiculing himself yet another time, congratulating you for your magnificence as a teacher and yet you on the other hand actually apologizing for being not up to par. Poor fellow, he is for ever betting on the wrong horse.
I have been very helpful giving you a very clear indication that you should have another look and consider the point of application of reaction force pairs. You nevertheless overlooked this very clear indication and seemingly needed another physics colleague to have this pointed out to you.
So we have seemingly made some progress. However, to my surprise you now come back with more faulty science and again with the help of an expert physics colleague. What on earth do they teach at Cambridge University? Is all talent perhaps gone to Oxford University?
So let’s try to further your education, enlighten your sleepy Cambridge colleagues and help possibly others a bit with all this confusion about centrifugal force.
Let’s have a closer look at the content of your last post.
Hence implied
-1-
Newton’s third law not to be valid, since denying existence of an action reaction force pair.
(blasphemy for a Brit/scientist; hope your students don’t know your screen name)
and clearly stated that
-2 -
Centrifugal does not exist.
Let’s resume the fundamental salient features of Newton’s third law.
-1-
It specifies the nature of force as existing in pairs of two equal but opposite forces. The existence of a single force is henceforth impossible.
-2-
The pair of forces acts on different bodies.
-3-
The two forces do not neutralize each other, acting on different bodies. Each will accelerate when free to do so.
Let’s do some very basic stuff by deriving Newton’s third law solely from Newton’s second law and show that it allows no exception , i.e.,
ALL forces come in the form of action reaction pairs in Newtonian Physics. Forces don’t have to interact by physical contact but can act also at a distance, thus including gravitational and electrostatic forces. You can see my
analysis here.
Your denial of the existence of centrifugal force is inherently implying the same a the first claim, i.e., denying existence of reaction force therefore also denying the validity of Newton’s third law.
Let’s start by stating that centrifugal force definitely does exist and is as real as is considered to be the centripetal force. Each is capable of producing acceleration. It keep surprising me to see scientific texts putting reaction forces, inertial forces and fictitious forces nonchalantly all in the same batch. In a sense you and your colleagues simply confirm convincingly the existence of this perpetual scientific confusion.
We are all familiar with various types of scales using springs to measure force. For instance when noting with disgust the needle showing the plus weight we are putting on every day or a fisher men hooking his big fish (caught not bought) onto his little weighing scale. Nothing esoteric just very basic stuff.
In Fig1 we have a spring measuring the weight of mass M. The deflection from neutral is a direct measure for the weight of the mass M. Using a free body diagram, Fig 2, shows ALL the forces acting on either the spring or the mass M. Being familiar a bit with springs measuring forces we will proceed to the next case.
The same spring mass ensemble is now positioned on a table with zero friction hence gravity is eliminated, Fig3. Imagine the spring to be housed in a tube with zero friction inside. Imagine the ensemble to be turning around progressively faster till a certain angular speed is reached. What happens? Correct, the mass M progressively moves away from the center of rotation till an equilibrium state is reached and henceforth the mass M rotates at a constant distance from the center.
Since the spring elongates a force has to exist acting on its end. It operates outwards along an action line through the center, one simply can’t escape this self evident conclusion. This force is indeed the poor centrifugal force, denied to exist by so many, sometimes in almost hysterical overtones. Its existence is as real as that of the centripetal force. It is a real force acting on the golfer in his swing.
Fig4 shows all the forces acting using free body diagrams. There is only one force acting on the mass M, the centripetal force which is produced by the spring. The centrifugal force is busy elongating the spring. The spring being stretched pulls back on both sides with an equal force. The action reaction force pair at the center does not cause motion due to restraint.
There is an intimate circular dance going on between the mass and the spring. The mass continuously ardently aspires to escape into the fascinating freedom of space. The spring deeply in love with the mass desperately hangs on. The mass pulling away, centrifugal force; the spring fighting back, centripetal force. Whenever you see the an object circulating, seemingly with no change, around and around, be aware there is more than meets the eye.
