Line of compression and tangential force
 

I've been really trying to get into chapter 2 with in respects to physics to really get into Homer Kelley's mind further beyond than perhaps the text of the golfing machine itself and fully appreciate it.

It is my understanding (and ive just started studying this stuff so its very probable I've got the wrong end of the stick) that if you whirl a heavy object in a consistant orbit that the velocity and its mass (force) of the object being whirled around is always tangential to the point that the object is on the circle. Like if the string was cut - the ball would fly off at 90 degrees to the line of the centrifugal pull out.....

What is puzzling me is at impact the line of compression looks more down the angle of approach in picture 2-C-3 instead of down the tangent of the orbiting sweetspot. I would of thought the line of compression would be tangential to the orbit at the the point that the sweetspot travels through the ball.

Why also is in the picture 2-C-1, the line of compression pointing downwards at low point in comparison to the picture in 2-A?

Any ideas

I am no physics expert, but this little tidbit may help:

The hook-face alignment of the Clubhead – designed to give it the proper relation to the Plane Line – diverts the ball from its true tangential path.

Im not 100% sure either, this is sure interesting though :). It is 'my thoughts'(for what their worth until I become more educated on this)is that the orientation of the clubface gives the 'point of compression' but the line from that point onwards through the ball is the clubhead force which is tangential to the sweetspot orbit. If the point of compression is not in a vertical axis, you get what you see in diagram 2-B. Whats your thoughts?

Now looking again at diagram 2-C-1 whilst typing this post. I missed that the arrow for clubhead force is tangential in the low point but it looks as though the LOC took the clubhead force from the original impact point and perhaps why it points downward... which would make sence as it is the point that the compression or distortion took place.... very interesting indeed...

Matthew.2-C-3 is the application of linear force for THE LOB SHOT using vertical hingeing and its associated clubface layback.In 2-C-1 the LOC is pointing down because the clubface is travelling downwards during the impact interval.In my opinion 2-A is showing a simple explanation of resilince without the additional confusion of the conditions shown thereafter.Remember LOC is not the line of flight.It may help to read 2-A.

Just one thing, I've read this book and the whole of chapter 2, which surprisingly also includes '2-A resilience' so much I can just about quote it all by memory. When someone says 'it may help to read 2-A' it really bugs the hell out of me...

I actually mean't 2-C-1#3.... it was accidental... I did not mean the lob shot pictures of 2-C-3....

I know the line of flight and the line of compression are seperate. You must take me to be a real idiot or something... That was not what I asked.....

My question is why is the clubhead force going down the angle of approach like in picture 2-C-1#3 instead of off a tangent of the circular clubhead orbit.

If the string gets cut the ball flies out in a straight line directly away from the source of the centripetal force that is trying to pull it inwards.

Not going to get into the TGM part of it, because I don't have the book here to reference, but from a physics view point...

Be careful with the words you use. Mass is not a force, never will be. An object when travelling in a circle will have instantaneous velocity at a tangent to the circle, and instantaneous force (and therefore acceleration) towards the centre of the circle, in your case this force is tension in the string.

When one cuts the string, that force towards the centre of the circle gets removed, therefore there is no force (and therefore no acceleration) on the rock, so you are correct, it will fly off tangential to the circle.

Will expand on TGM side of it once I have the book in front of me (don't have the diagrams memorised yet..sorry)!!

Call the physics police
 

No it does not.

Just my 2 cents, but I thought the reason Homer drew 2-C-1 #3 that way was to illustrate that both the angle of approach and the arc of approach methods of delivery will give a straight-away golf shot.

In ideal compression, the ball will not leave the clubface instantaneously, but after the ball has reshaped. Then the internal forces causes the ball to propel along the line of compression. (2-A)

The diagram illustrates why we have to hit the inside-quadrant to get a straight shot. The distance in the arc is the distance the clubhead will travel during the time the ball deforms and reforms. (In reality, that distance isn't very long, just exaggerated in the diagram to give room to see everything.)

BTW, have to check my physics books, but the circular motion of an object gives it a tangental and radial force. The combination is why an object will go in a circle and not either drive into the center or fly off in a tangent. When the circular force hits an independent object, the force calculation on the ball would be (the mass of the clubhead) X (tangential acceleration)

A object travelling in a circle does NOT have tangential force.

Force gives acceleration. If it had tangential force it would go faster or slower around the circle.

Isn't centripetal force a radial force:confused: Probably should have said centripetal acceleration to be clearer. I think what you are describing is angular acceleration. But as I said, I'm at least 15 years from my last thoughts about physics.

I am an idiot, I meant tangential force...an object moving in a circle does not have tangential force, as that creates angular acceleration...it does have radial force and acceleration...otherwise it would go straight!

From the website http://www.fearofphysics.com/BallString/ballstring.html

Look at the pictures here

Which way?

I think I have to look at this right from the beginning. I need to look at terminology, so im going to make sure I have these concepts and ill just paste them as I look them up to save anyone else interested the time...

- The line of compression is the direction of the impact force.
- Force is the capacity to do work or cause physical change; energy, strength, or active power.
- A Force is equal to mass times acceleration per newtons 2nd law
- Acceleration is the rate of change of velocity with respect to time.
- Velocity is a vector quantity whose magnitude is a body's speed and whose direction is the body's direction of motion.
- Vector is a quantity, completely specified by a magnitude and a direction.
- Magnitude is the greatness in significance.

Ok question time relating to these terms....

To maintain a certain velocity of anything, it is always accelerating ?

For a given force when a collision occurs, the force transfered by the acceleration really means the velocity created by that acceleration at that moment in time?

A ball whirling around like in my picture post above - since the velocity or acceleration (discounting the other forces just now) is always tangential to the orbit, then the force of that ball hitting anything (tangential force I assume) is also going to be tangential to its orbit?

and if this is true - then the direction of the clubhead force (keeping the clubface seperate for just now) traveling in its orbit should be tangential to the clubhead orbit?

Hope that clears it up a bit?

It helps yes :)

I have to go to bed just now will read it a few more times when I wake up :)

Matthew I definately do not think you are an idiot.I was merely responding to your post,which was, I thought, most interesting as this aspect of the book is seldom discussed.I am sorry you took offence as none was meant.I am not trying to make an excuse but originally my post was much longer,but when Itried to preview it ,a note came up saying it was an "invalid thread "or something like that (maybe admin can look into that as it has happened before)I was a little pushed for time so I posted the short thread which does sound a bit condescending in hindsight .I assure you I was only trying to help.

Its ok, its probably not just you, I had just woken up also so I was probably 'crabby' mood anyways.

Anyways looks like my sleep after the nightshift isn't happening so I might ask some questions just now....

I didn't do physics at school past standard grade and just passed that and no more just using common sence and pretty much no study other than knowing speed=distance/time...lol. I was good with maths though which helped some....but im a REAL newbie at this...

I am very confused with the two. Velocity to me has always been pretty much completely interchangable with speed - is that correct ?

I have always seen it as the faster the speed and the more heavy the weight of an object hitting another object, the more it the second object moves. But with F=ma newtons second law, it confuses me....because it is not the velocity but the acceleration and like you said 'a constant velocity (speed I think...) means no acceleration which results in no force via the equation. If two rocks in space(just to get rid of other forces at the moment) are traveling at a speed or velocity but not accelerating, it appears to me that their should be force applied on to the other. Kinda like if you hit a cue ball in pool and its slowing down to a crawl where it seems to be deaccelerating, it will still give force to the object ball. Im just very confused and I know Im not right here but this is the way im thinking....where am I going wrong ?

Remember it is net force that matters, not any old force. For example, if I am pushing a box forwards on a table at a constant speed, I have to apply force to push it forwards. According to the equation F=ma, there would be acceleration (a=F/m). But because F refers to net force, acceleration is zero. The frictional forces between the table and box cancel out (vector sum of forces equal to zero). When forces are balanced, there is no change in velocity (this does not necessarily mean 0m/s), hence acceleration is zero.

You can maintain a constant speed of something and still make it accelerate, as in circular motion. But you can't maintain a constant velocity.

Interesting choice of words given their 'relative' gravity. ;)

Velocity is a vector.

You can think of Velocity as a Speed with a Direction.


A rock whirling on a string is always Accelerating because it's constantly changing its Direction.

As others have said, velocity is speed with direction. So an object moving in a circle at constant speed will have a constantly changing velocity as the direction is changing. Think of a car driving a straight bit of road. If it drive 10mph along the road, then does a U turn and drives 10mph back down the road the speed has been the same both ways, but the velocities are the exact opposite of each other.

Use the two balls floating in space, towards each other. While they are floating (at a constant velocity) there is no force on either, hence no acceleration. Now, once these two balls collide with each other, as soon as they touch, they apply a force to each other, and therefore accelerate each other. This is where the F=ma comes into it. Throughout all collision there is energy conservation. That is the energy in the initial system will carry through to the final system. The initial system will have the kinetic energy (1/2 * mass * velocity^2) of both balls, during the collision some energy is given out as sound, the final system will then have the remaining energy still as kinetic energy of the 2 balls.

As another way to think of it. A ball sitting still in space weighing 100grams, and a block weighing 1kg approaches at 10m/s. Assume a perfect collision (no energy as noise, heat etc). Initial kinetic energy in the system is all in the block (.5 * 1 * 10^2 = 50 Joules). Assume during impact the collision causes the block speed to halve to 5m/s it now has energy of (.5 * 1 * 5^2 = 12.5 Joules), this leaves 50 - 12.5 = 37.5 joules of energy for the ball.

Using the KE=.5 * m * v^2,

37.5 = .5 *.1 * v^2
v = 27.4 m/s

Not sure how this helps a golf swing, but hope it helps with the physics you are trying to understand.

I am trying to understand what it is we are talking about here Matthew.Is it the clubhead or the ball?

It will help my understanding of the physics behind the golfing machine, once I have a better understanding of physics as a whole....to understand the forces at work, I will appreciate certain perspectives that Homer talks about.

I kinda understand your answer, but I think it mostly shows I have no real knowledge and I have to spend a few days studying it - since my last post I bought 'physics for dummies'..lol for a start and will read it pretty soon.

Thank you for your answers they have been appreciated.

Matthew ,Hope you've slept well! I think (without being presumtuous)that you are looking at the angle of approach without taking into account the closing of the clubface.If you look at 2-C-1#3 both the angle of approach and the arc of approach give a staightaway line of flight (tangential to the clubhead arc of approach at separation )but this is using Dual Horizontal Hinge Action ,so may not be for hitters.Hope this helps