Couple why questions

[iacas]

my hypothesis is that at the moment of impact, when the clubhead makes a contact with the ball below the equator cleanly, there is enough of a downward force on the ball and the scale will register a higher weight for a split moment than the original ball weight, suggesting that at impact there is an additional force into the "ground" that the ball sits on, thus a reaction if one looks the other way, which helps explain the well known yet fuzzy term, uh, compression...

Your hypothesis is wrong. The ball immediately begins going upwards, away from the ground, on any shot in which the club impacts the ball below the equator.

"Compression" is against the clubface, not against the ground. Pros and good players will often say they like to "pinch" the ball against the ground or other variants, but that's just a feeling, not a reality.

unless such an experiment (or a similar one) is done, it is geeks' playground in the air...aka, anyone is entitled with an opinion

It's not an opinion when a fact is involved. Fact: the ball doesn't exert a downward force on the ground when it's struck below the equator in a real golf shot.

Even if you think the ball exerts a downward force because it compresses a little and thus becomes slightly more oblong, you'd be wrong because the ball lifts and rolls up the clubface more than it compresses. The only time even this might work is when you strike a ball at 100+ MPH with a driver that has no loft at impact, but then you'd be violating the "beneath the equator" tenet anyway... Maybe with 0.1 degrees of loft, but that's awfully hair-splitty and not at all a "real golf shot." I understand what you're trying to say, but go look up BizHub SwingVision shots of the ball impacting with clubs or something. I've also seen these studies done by club manufacturers... the ball doesn't go down first.

[wedge player]

so here is a theoretical question, possibly a clinical question that can be verified if proper set-up can be arranged...

think of a tee it doesnt get hammered down while the ball is on top of it that is proof there is no downward force

[golfdad]

iacas, your points are well taken...

on the scale experiment, it will be also interesting to see how the scale reacts 3 wood vs sand wedge...

on the lingo, i have heard teachers using the phrase,,,to compress the ball into the ground, as you said, to pinch.

agree, during impact, the ball is compressed by the clubface.

[VOX]

The first one is just dumb. And I've never heard anyone say it. The second one seems true just from physics. It might also be true that it does something to the mechanics of the air flow and increases lift, but it seems a tail wind would decrease the force of the air through which the ball has to travel right off the club, and then as the ball decelerates the wind would actually be pushing from the back, and push the ball forward as it comes towards the landing zone.

The two are actually somewhat similar. In the first case, the ball tends to run more because it has less backspin (not topspin). In the second case, the ball is almost always traveling faster than the air (except for some rare lob shots etc.) so it has less resistance, but still has resistance.

[golfdad]

"think of a tee it doesnt get hammered down while the ball is on top of it that is proof there is no downward force"

good point.

as i said earlier, i have problem accepting this in a black or white fashion. common sense is very important but often we need empirical data to be sure. perhaps that is why there is that show on discovery channel to explore some everyday truism...

mind you, this is not a situation where a ping pong ball is struck with a spin in the midair. when a golfball is struck with a club, it is resting on something and between the ball and that something is friction...

perhaps the tee is lowered just a tiny weeny bit that human eye cannot detect,,,

disclaimer: my opinion has not been proven to be fit for human consumption:)

[groovezilla79]

It's not an opinion when a fact is involved. Fact: the ball doesn't exert a downward force on the ground when it's struck below the equator in a real golf shot.

Just like to back this statement a little. If the golf club literally compressed the ball into the ground then there is no way anyone, pro or otherwise, could play in wet/rainy conditions. The ball would just sink into the ground at impact.

[golfdad]

http://en.wikibooks.org/wiki/A-level...ce_as_a_Vector

[ballhog]

......could be a stupid question, but....why the hell are you hitting off concrete anyway?

[safetrip]

its a difficult shot because you have little room for error in both situations. where as with a good lie on the fairway you can hit the ground a little early and not lose much club speed and strike the ball well but in sand you would lose to much club speed and hit a short/fat shot.

I completely agree with this answer. "picking up clean" doesn't necessarily mean you don't have any divot but it is trying to emphasize that you really have to hit the ball first. The other thing that "picking up clean" will do compared to "compressing down" shot is that it will give you more distance and that's what you usually want in the fairway bunker.

BTW, this reminds me again of a golf fallacy- you compress the ball by :trapping the ball between your iron and the ground". If you really trapped a ball between your iron and ground, it's really trapped. It's not going to fly out into the sky. The ball doesn't bounce off the ground. It bounces off the club head just like you cut a ball to pop in the air in ping pong or tennis.

[safetrip]

"think of a tee it doesnt get hammered down while the ball is on top of it that is proof there is no downward force"

One experiment you can do with a tee is next time you are on the range, tee up a ball but tilt it as much toward the target as you can before the ball slips out. Then hit the ball with an sand wedge with as much 'descending blow' as you can. If there was any slightest amount of downward force like you said, the ball doesn't have any other choice but drop on the ground.

[golfdad]

thanks for that suggestion. unfortunately, i am not good enough of a golfer to swing sandwedge at an accuracy that can be considered scientifically reliable i'd hate to introduce operator error and to be another confounding variable...

allow me to clarify. by downward force, i did not and do not mean 100% of the force, but a vector, aka, a percentage of it because the angle of attack is not purely forward toward the target, nor purely downward toward the center of the earth. in addition, ideally, the sandwedge strikes at the tanget of the sphere of the ball, not directed directly at the center of the ball.

however, even if the tee is slanted so much that the ball is just about to fall off, at that instant, there is still contact and friction between a portion of the top of the tee and the ball. because this physical relationship exists, when another force (via the sandwedge) is applied to the ball, a vector of that force should apply to the tee as well... IF the top of the tee receives a teeny weeny bit of the downward blow, then, based on the physics principle that for every action there is a reaction, the tee pushes up on the ball with that same teeny weeny vector, thus an upward pinch, or compression:)
. i am really blushing because this is very geeky!

[verse214]

This leads into a question I've had for a while:

Since there is no downward pressure on a ball when it is struck with a golf club, why do "they" (yes, the man) teach you to always try to hit "an inch behind the ball" in a greenside bunker? I can understand why you'd do this if the ball is partially embedded in the sand, but doesn't this mean that if the ball is sitting cleanly in a greenside bunker, you can strike the ball as if you were chipping or pitching from the fairway?

[zeg]

This leads into a question I've had for a while:

It's a lie. It's the Man keeping you down.

I believe it's because in well-maintained bunkers you're rather unlikely to frequently encounter a completely clean lie. In the hard sand bunkers I play this happens a lot, but if the sand is soft and fluffy usually you'll be at least partially sunk. If you really have a completely clean lie, go for it I guess. In my experience, the kind of sand that gives you a lie like that is hard enough that the blast is not going to work anyway...

[safetrip]

you can strike the ball as if you were chipping or pitching from the fairway?

You can except that the ball won't pop up 6' high to go over the mound in front of you. I think hitting exactly 4 inch behind ball is not as important as you make sure open the face and glide underneath the ball to pop it out. Since the angle of attack is so shallow, the club face needs to enter the sand first to insure that it is gliding below the ball with some margin of error.