[IKE]

Mass of a kicker is important to a point. the kicker and the ball need to be in the same order of magnitude otherwise there are different governing equations.

Think of it in terms of tiny mass or really big masses. The ball itself weighs about 0.5kg or roughly 1.25 lbs. If your kicker is really light. Like 1.25 OZ. then in order to impart the kinetic energy needed on the ball it will need to go at sqrt(16) or 4 times the speed. This is really fast. If we go a step further, then say about 1/16th of an ounce, then it would need to be another 4x of 16x faster. For something this light, it would have to go really fast and might puncture the ball. Thus more surface area would be required, and it would loose a lot to areo losses before striking the ball.

Now go the other extreme. Say you use a 16 lbs sledge hammer. From an energy standpoint, you would only need to go 1/4 the speed for the ball, but in this senraio you would likely just push the ball instead and not get a big kick out of it.

Too little and it is difficult to store and transmit enough kinetic energy. Too massive and it is difficult to get the mass up to an effective speed.