In the interests of promoting golfers' understanding of physics and
thereby enhancing their game, I feel compelled to comment on a minor error
in the interesting case report by Buchanan et al. The authors explain the
regulation maximum coefficient of restitution of a golf club of 0.83 as
meaning that a club head velocity of 100 mph will cause the ball to travel
at 83 mph. However, if this were true, the club head would have to either
pass through the ball, or decelerate quite substantially to less than the
ball's speed, resulting in a very nasty kickback to the golfer's arms.
In fact the coefficient of restitution is calculated by (V2f -
V1f)/(V1 - V2) where V1 and V2 are the scalar velocities of the two
colliding objects (here, the club head and ball) before impact, and V1f
and V2f are the velocities of the respective objects after impact. Using
this formula we find that a golf club head with a coefficient of 0.83,
travelling at 100 mph, will impart a velocity of 183 mph to a golf ball,
assuming zero deceleration of the golf club at impact (which is fairly
safe where one object far outweighs the other).
Competing interests:
I share Mark Twain's view on golf, and hope that the association of perplexing calculations with the sport may act as a form of aversion therapy, and hasten its extinction.
Rapid Response:
Coefficient of restitution
In the interests of promoting golfers' understanding of physics and
thereby enhancing their game, I feel compelled to comment on a minor error
in the interesting case report by Buchanan et al. The authors explain the
regulation maximum coefficient of restitution of a golf club of 0.83 as
meaning that a club head velocity of 100 mph will cause the ball to travel
at 83 mph. However, if this were true, the club head would have to either
pass through the ball, or decelerate quite substantially to less than the
ball's speed, resulting in a very nasty kickback to the golfer's arms.
In fact the coefficient of restitution is calculated by (V2f -
V1f)/(V1 - V2) where V1 and V2 are the scalar velocities of the two
colliding objects (here, the club head and ball) before impact, and V1f
and V2f are the velocities of the respective objects after impact. Using
this formula we find that a golf club head with a coefficient of 0.83,
travelling at 100 mph, will impart a velocity of 183 mph to a golf ball,
assuming zero deceleration of the golf club at impact (which is fairly
safe where one object far outweighs the other).
Competing interests:
I share Mark Twain's view on golf, and hope that the association of perplexing calculations with the sport may act as a form of aversion therapy, and hasten its extinction.
Competing interests: No competing interests