A golf ball is 1.68” in diameter and the average club golfer generates a club head speed with a driver of around 85mph. When club head meets the ball at impact the surface area of the ball is the approximate size of a 10 pence coin and despite what manufacturers would have you believe, the sweet spot on a clubface isn't a great deal bigger.
When you factor in the average arc your clubhead travels with a driver from address to impact is approximately 8 yards, you must be very precise to strike a shot from the middle of the sweet spot and maximise the transfer of energy. If that isn’t enough, to strike a straight shot the clubface needs to be aiming at your intended target, travelling in the direction of your intended target and on a good angle of approach for that ½ millisecond that the ball comes into contact with the clubface.
FACTORS AT IMPACT
Where the clubface is aiming at impact has the largest influence over the direction of your shots. A ball struck in the centre of the clubface will leave closer to the direction it is facing rather than the direction it is travelling in.
Curvature in ball flight occurs when there is a difference between where the clubface is aiming and the direction it is travelling at impact (the path). The bigger the difference the bigger the curve and shots will fly.
ANGLE OF APPROACH
We play shots whilst standing to the side of the ball so our swing arc of swing will be at an angle of approximately 45 degrees to the ground. Approaching the ball from too far above or below this will cause you to strike too down or up on the ball at impact.
CENTEREDNESS OF STRIKE
When the ball is struck on the toe or heel of the clubface there will be less resistance on the opposing side which will cause it to overtake and miss align the clubface. Heel strikes will close the clubface and toe strikes will open the clubface.
If all of the above are correct then the faster a club travels at impact, the further the ball will travel. Faster swing speeds generate more spin and there will be more curvature in flight if there is a difference between where the club is aiming and the direction it is travelling in.