Followers 0

# Physics

## 43 posts in this topic

I love physics, but when you post something as dumb as

this , you force me to comment:

Q - If a 6'2" golfer swung at 120 mph, would his ball fly farther than a 5'6" golfer swinging at the same speed? All other things being equal, is this correct? --------------------------------------- A - No, the mass and acceleration in "mass times acceleration" is the mass and acceleration of the club. All things being equal, a 120 mph club swung by anybody is a 120 mph club to the ball regardless of the person hitting it. The velocity of the ball is related to how well the momentum of the club is transferred to the ball. However, in order to accelerate the club, a 6'2" person will use less muscle to get the club up to speed compared to the 5'6" person. That is the mechanical advantage of the moment arm that you mention. Hope this helped.

I responded:

I should have said the shorter person actually has to accelerate more quickly... since he has less distance through which to achieve the speed. Though that's only if players swing at the same tempo...

0

##### Share on other sites

There are so many variables in relation to the golf swing. I was walking through the golf section of my local book store and stumbled across a book called The Physics of Golf and just skimmed through it and it looked ridiculous. I'm in Physics right now and whenever we learn new material I think about how it relates to either the golf swing or ball flight, etc.
0

##### Share on other sites

Just hit the friggin' ball for hells sake!
0

##### Share on other sites

Just hit the friggin' ball for hells sake!

No kidding! Jeez, talk about paralysis by analysis.
0

##### Share on other sites

No kidding! Jeez, talk about paralysis by analysis.

Uh, some people enjoy thinking about and discussing the physics of the game. After all, where would the game of golf be

without an understanding of physics? Not very far. We still might be using dimple-less balls and groove-less clubs. Just because y'all don't want to participate in a physics discussion doesn't mean ya need to knock it. Some people enjoy it. A few less than that actually make their living off of it.
0

##### Share on other sites

Hi Erik,

This is Matt from GolfTimes.blogspot.com. Thanks for the reply to my post but I'm a little confused as to why you say it's a bad answer and misleading.

First let me say that I didn't ask that question and Chris Murphy,P.E. answered it but I do agree with his answer. Also, I think the question itself was hardly worth asking because as I alluded to in my post , 120 mph is 120mph no matter how you got there, whether you use acceleration or velocity. That is assuming everything else is equal as the person who asked the question stated.

Now, on to your response. Let me respond to the first part (reprinted below):

"Not only can people accelerate at different rates and arrive at the ball at the same speed (120 MPH), but it doesn't matter much how tall someone is in regards to acceleration."

I agree with both parts of this sentence if you assume if everything is equal. It doesn't matter at what rate you accelerate if you arrive at the ball at 120 mph it's 120 mph.

Next part:

" Finally, a taller person likely has longer arms, too, and since arms weigh more than a club's shaft, the taller person has to accelerate more weight to the same speed. Thus they actually likely do more work than the shorter golfer. "

I agree that a taller person has longer arms and that they weigh more but I would disagree that he has to work harder to accelerate to 120 mph. You pretty much make my point in your next paragraph:

" The real advantage taller golfers have is that their swing radius is longer. If they can pivot angularly at the same rate as a shorter person, the clubhead (at the outer end of the radius) moves faster. "

A taller golfer naturally creates a longer swing arc and therefore will create a greater centrifugal force than a shorter person which means he would not have to work as hard to get the clubhead to 120 mph than a guy who has a shorter swing arc. Don't foget that everything else is equal according to the original question.

" I should have said the shorter person actually has to accelerate more quickly... since he has less distance through which to achieve the speed. Though that's only if players swing at the same tempo... "

This statement further validates my statement that the shorter guy has to work harder to accelerate his club to achieve the same impact speed as the taller golfer.

Did this make any sense or are we still standing on the opposite sides of the fence?

0

##### Share on other sites

I agree with both parts of this sentence if you assume if everything is equal. It doesn't matter at what rate you accelerate if you arrive at the ball at 120 mph it's 120 mph.

Acceleration doesn't stop at the ball and since the ball is in contact with the club face for a few thousandths of a second, the rate at which the club was accelerating prior to impact plays a role in how far the ball will go. Which would be a nod in the direction of the shorter player, since he would have had to accelerate at a faster rate to reach 120 by impact. However, the longer swing radius of the taller player allows the ball to remain on the club face a little longer, basically nulling this point of the argument.

"

Touché

"

There is no such thing as centrifugal force. That "phenomenon" is just Newton's First Law (An object in motion tends to stay in motion...) in relation to radial motion. The actual force you're referring to is Centripetal Force or the force directed inward from the apex of the arc (from the clubhead to the grips in this case). I know, it seems to make absolutely no sense, but its true.

0

##### Share on other sites

Hey Jeff, good job on the explanation. I don't know if your right or not but I'll assume you are because it sounded good. BTW, Erik made a reply on my blog ( www.golftimees.blogspot.com ) and I responded to him which I'm not sure made total sense but you can see it for yourself if you like.

Erik, let me know what you think.
0

##### Share on other sites

Hey Jeff, good job on the explanation. I don't know if your right or not but I'll assume you are because it sounded good. BTW, Erik made a reply on my blog (

I think that without an understanding of physics, it's tough for you to debate this topic, just as I think it was irresponsible (though very mildly so) to post it to begin with.

0

##### Share on other sites

Newton, a great physicist, said three things regarding all motion...

One - A body at rest stays at rest and a body in motion stays in motion,

with uniform velocity, unless acted upon by an outside force.

Two - The acceleration of a body is directly proportional to the force applied

to it and inversely proportional to its mass.  This just means more force yields

greater acceleration and vice versa.

Three - If a force is applied to a body, the body simultaneously exerts a force

of equal magnitude and in opposite direction to that which applied the force.

Swing speed and momentum, believe it or not, have nothing to do with how far the ball will go.

What makes the ball accelerate off the tee is force applied to the club.

Greater force means greater acceleration.

Suppose one man hits the ball twice as fast as another, yet both with

equal force; both balls will travel the same distance, all other things being equal

(all other things are not equal if there is variation in the direction the force is applied

to the ball).

This seems to indicate that shortening the back swing and applying more force to the club

shortly after the downswing begins, makes it easier to hit the ball in the right direction.

But I wonder, is it uniform force (uniform acceleration) that one seeks or is it

a gradual increase in force (acceleration of acceleration)?

In any event, I think it's very clear de-accelerating in the downswing results in pitiful shots.

0

##### Share on other sites

When I read Erik's (7 year old !!!!) OP the first thing that popped into my head was that this silly question is just the "what weighs more, A pound of rocks or a pound of feathers?" Trick question twisted into a golfing scenario. :)
0

##### Share on other sites

Got to love collisions, acceleration means nothing in impacts, all it dictates is possibility for higher or slower velocity, which governs the physics on this point.

Is there a correlation between height and golf ball distance, yes, but its because they just have an advantage in being able to generate speed with less effort (body rotation)

0

##### Share on other sites

Newton, a great physicist, said three things regarding all motion... One - A body at rest stays at rest and a body in motion stays in motion, with uniform velocity, unless acted upon by an outside force. Two - The acceleration of a body is directly proportional to the force applied to it and inversely proportional to its mass.  This just means more force yields greater acceleration and vice versa. Three - If a force is applied to a body, the body simultaneously exerts a force of equal magnitude and in opposite direction to that which applied the force.  Swing speed and momentum, believe it or not, have nothing to do with how far the ball will go. What makes the ball accelerate off the tee is force applied to the club.  Greater force means greater acceleration. Suppose one man hits the ball twice as fast as another, yet both with equal force; both balls will travel the same distance, all other things being equal (all other things are not equal if there is variation in the direction the force is applied to the ball). This seems to indicate that shortening the back swing and applying more force to the club shortly after the downswing begins, makes it easier to hit the ball in the right direction. But I wonder, is it uniform force (uniform acceleration) that one seeks or is it a gradual increase in force (acceleration of acceleration)? In any event, I think it's very clear de-accelerating in the downswing results in pitiful shots.

You're misapplying F=ma here. You'd be better served using impulse-momentum dynamics (another result of Newton's genius).

0

##### Share on other sites

The reason is, when they figured out Momentum, it includes force. What happens is, in the derivation for the momentum equations, its simplified to mass x velocity

So it does incorporate F = ma, but acceleration isn't used in its final form. This proves in the collision between a clubhead and golf ball its velocity that matters, not acceleration. You will find in physics that acceleration isn't used much. The reason is, that a lot of equations are simplified and combined into simple terms.

This is why a bullet does damage to the body, not through mass, but by velocity. When a bullet hits you, its doing 0.5*M*V^2 energy on the other body. So when a bullet hits you, its not accelerating, in actually its deaccelerating, because the initial velocity is less than the final velocity when it hits you. So acceleration is negative. So, as you can see, in impacts, its velocity not acceleration, if so then guns would do shit damage :p

0

##### Share on other sites

Originally Posted by saevel25

The reason is, when they figured out Momentum, it includes force. What happens is, in the derivation for the momentum equations, its simplified to mass x velocity

So it does incorporate F = ma, but acceleration isn't used in its final form. This proves in the collision between a clubhead and golf ball its velocity that matters, not acceleration. You will find in physics that acceleration isn't used much. The reason is, that a lot of equations are simplified and combined into simple terms.

This is why a bullet does damage to the body, not through mass, but by velocity. When a bullet hits you, its doing 0.5*M*V^2 energy on the other body. So when a bullet hits you, its not accelerating, in actually its deaccelerating, because the initial velocity is less than the final velocity when it hits you. So acceleration is negative. So, as you can see, in impacts, its velocity not acceleration, if so then guns would do shit damage :p

I am not misusing Newton's second law that says F = ma

While it's true momentum is a product of mass and velocity and is conserved over collisions.  It is also equal to the magnitude of force applied to a body and the duration of time it's applied.  Since you can't do anything to about the time applied, the only thing that matters is force.  Force is directly proportional to acceleration and causes acceleration in other bodies and not the other way around.

A bullet causes damage, not by its velocity, but because the human body applies a force on the bullet to stop it - see Newton's first law.  Since the area of the resulting opposite force is so small, it causes tremendous damage; that is why law enforcement officers wear kevlar vests, as it spreads the energy out over a greater surface area.

If you believe momentum or swing speed is desirable, and not acceleration of the club head, think of this...  suppose there are two golf balls suspended in front of a large moving train  traveling with uniform velocity and a small sports car accelerating quickly; both strike the ball at the same speed.  The momentum of the train is huge, yet the momentum of the car is small in comparison; The car will knock the ball much further than the train.

Else, just de-accelerate slightly on the down swing and tell me about the shot.

0

##### Share on other sites

While it's true momentum is a product of mass and velocity and is conserved over collisions.  It is also equal to the magnitude of force applied to a body and the duration of time it's applied.

0

##### Share on other sites

Originally Posted by Michael Lee

While it's true momentum is a product of mass and velocity and is conserved over collisions.  It is also equal to the magnitude of force applied to a body and the duration of time it's applied.  Since you can't do anything to about the time applied, the only thing that matters is force.  Force is directly proportional to acceleration and causes acceleration in other bodies and not the other way around.

F=ma is best applied to determine how much force our muscles need to exert to cause the clubhead to arrive at the ball at a high rate of speed.

How much farther does a golf ball travel when hit with the exact same impact conditions, but one clubhead is accelerating and another is decelerating. I'll spare you the thought: you won't be able to tell the difference in any real world tests, even on the calmest of days.

Originally Posted by Michael Lee

A bullet causes damage, not by its velocity, but because the human body applies a force on the bullet to stop it - see Newton's first law.  Since the area of the resulting opposite force is so small, it causes tremendous damage; that is why law enforcement officers wear kevlar vests, as it spreads the energy out over a greater surface area.

You like to look at things backwards, don't you? The body isn't applying the force. The bullet is the one with the velocity. It applies force to the flesh/bone/etc., the body reacts.

Originally Posted by Michael Lee

If you believe momentum or swing speed is desirable, and not acceleration of the club head, think of this...  suppose there are two golf balls suspended in front of a large moving train  traveling with uniform velocity and a small sports car accelerating quickly; both strike the ball at the same speed.  The momentum of the train is huge, yet the momentum of the car is small in comparison; The car will knock the ball much further than the train.

No it won't. The impact interval is far too short for any acceleration to matter.

Here's a question for you: If you were to stick your hand out and smack a solid metal plate as it whizzed by you, would you rather that plate be attached to a high-speed train traveling at 300 MPH, or a sports car that can hit 60 MPH in 2.3 seconds (26 MPH/sec) 20 feet from where it starts off at a stop?

If you like your hand, you'll take the sports car every time.

0

##### Share on other sites

Quote:
Yes, and that's impact/momentum dynamics. ∆P = m∆V = F∆t.

Here's the thing

m*(v1-v2) = m*a*(t1-t2)

So you get Change in velocity = Acceleration * change in time, basic definition of velocity and acceleration.

So while you want to include acceleration, your basically already did because velocity accounts for it. The thing your doing is transforming velocity into acceleration by its basic definition. So acceleration doesn't add anything to the situation. The reason is your adding in time, so it all equals out. The math there proves it, your saying.

m*deltaV = m*a*deltaT

So there EQUAL. Meaning acceleration can't add anything more to the system because its equal to the other side. You can't just throw acceleration in. Because there is no other term there. There equal.

0

## Create an account

Register a new account

Followers 0

• ### Topics Being Discussed Right Now on The Sand Trap

• #### y men. They easily can't develop h

By trimjuriya, in Golf Talk

• 0 replies
• 0 views
• #### Modern course design. Do they really expect us to walk these things?

By Buckeyebowman, in Golf Courses and Architecture

• 49 replies
• 2,025 views
• #### 2016 BMW PGA Championship at Wentworth

By Scotsclaff, in Tour Talk

• 13 replies
• 186 views
• #### Scientific Studies

By saevel25, in The Grill Room

• 10 replies
• 188 views
• #### "Swing Machine Golf" by Paul Wilson

• 161 replies
• 59,787 views

• Want to join this community?

We'd love to have you!

• ## 2016 TST Partners

• ### Posts

• y men. They easily can't develop h
Growing a beard can be troublesome for many men. They easily can't develop hair in any length without it itching beyond Beard Czar grows mighty or lengthy ample to particularly qualify as a healthy beard. Now you will have the capability to develop that beard with the aid of beard progress serum. The elements on this product will help to leap-start the beard growth, despite the fact that you're for your forty’s or 50’s and have never grown a beard earlier than or just growing your first facial hairs. We will be able to talk about how the beard growth serum can help with beard progress, how you can use the product safely, and which are the great in the marketplace today. http://drozforskolin.org/beard-czar-reviews/
• Modern course design. Do they really expect us to walk these things?
Thanks to Whistling Straits there is now a move in Wisconsin to build courses that are walking-only. Erin Hills, the site of the 2017 U.S. Open, has to be walked. http://erinhills.com/ And now, Ben Crenshaw is trying to re-create Bandon Dunes ... http://www.sandvalleygolfresort.com/
• 2016 BMW PGA Championship at Wentworth
Many years ago while on a business trip to London I got a chance to play Wentworth West - even back then in 1991 it was a tremendous course that made great use of the rolling woodlands in Surrey. Its a bit sad that the course has now become the architectural plaything of Ernie Els and the European tour - some of the holes now resort to certain modern tricks like artificial water features or shaved greenside banks leading to hazards or chipping areas - perhaps in the next round of changes Ernie and his design elfs will come a bit more to their senses and let the design return a bit more to the features that were there in the original HS Colt design. As far as the tournament goes, it seems like there is a real problem in terms of when to fit it in a place in the schedule where you can get the cream of the European tour to show up.  The Players Championship with its huge reward of 10 years of exemptions for the US tour makes it a bit more compelling as an event and the Nelson and Colonial and Memorial tournaments are all big events on the US tour leading up to the US Open so taking the two weeks time to travel over to England in the start of the summer is perhaps not something a lot of European pros who live in the US are willing to make.  Was exciting to see if Chris Wood was going to choke the event away but nice to see him win - he did have a great front nine but seemed on the verge of letting it get away on the back nine.
• Scientific Studies