Re: Heavier club head = ball goes farther?
I can't help but weigh in here.
First of all mass does matter! Just watch the collision of golf ball and bowling ball here. Notice how much faster golf ball moves compared to bowling ball after collision.http://demo.physics.uiuc.edu/LectDem...re%20info.html
Assuming a frictionless, one dimensional world, when two rigid objects collide, their momentum preserves. Momentum=Mass*Velocity. (BTW Force=Mass*Acceleration but that's less relevant to golf swing). What this means is if the golf ball and club head have the same mass, a 100mph swing will give 100mph ball speed. But if the club head mass is 1.5 times the golf ball, the ball will fly at 150mph even with the same swing speed.
However, a golf ball is not completely rigid, nor is the face of the driver. Both of them will compress and expand during collision. In this case, Energy is preserved not momentum. (Kinetic) Energy=mass*Velocity^2 Here comes the velocity squared. But don't be mistaken to think that velocity is more important due to the square. It applies to both the club head and ball's speed. So the swing speed increase translates into similar amount of the ball speed if the mass is similar.
So the point is that club head weight and speed has the same amount of importance to ball speed. However, as some people pointed out, it's harder to swing faster with heavier swing weighted club(please note below that swing weight and club head weight are different). But it is also true that if the swing weight is too light, you cannot accelerate through the impact. Just grab the driver the other way around and swing it. You can't really swing fast. That is because there is impedance mismatch. The biomechanics of your body requires some amount of inertia when trying to swing a club. If the inertia(resistance or impedance) of the object you are trying to swing is too big, you won't be able to transfer maximum energy into it. By the same token, if the inertia is too small, you won't either. There is optimum amount of intertia- in this case, right swing weight for you to maximize the energy transfer between your arm movement and club head. But I'm willing to bet that right swing weight is different for different people- heavier/stronger person will be better matched with heavier swing weight.
One other thing to note is that just because the driver head is lighter doesn't mean that your swing weight is lighter too. If that lighter driver head is matched with even lighter shaft, the swing weight may increase. So I wouldn't necessarily conclude that modern day drivers' swing weight is lighter than older ones because the shafts became lighter too.
Bottom line is you want to experiment with different swing weights and see if what works better for you. I know KJ Choi sticks some lead tape on his irons because he likes the heavier feel of it. It may also change over time too. I personally happened to get two different swing weighted hybrids earlier this year- D3 vs D4 I think. In the beginning, when my body muscle wasn't ingrained with golf swing, I liked the lighter one but these days I like heavier one better. I haven't measured it yet but I wouldn't be surprised if I can actually swing the heavier one faster.Would you rather be hit by a 100-pound object traveling 1 MPH or a 1-pound object traveling 100 MPH?
I have to say this is not relevant, if not misleading example. Let's say you put on a 12 century steel armor and skate board. Both of above hits will move your body at exactly the same speed- a rigid body collision example.