In the dying moments of the First Cricket Test match for this season between Australia and New Zealand, one of the TV commentators remarked that the Australian bowler Mitchell Johnson was noted for being able to produce a ‘heavy’ ball. This, he said, was a ball that seems to hit the bat harder than its 140kph nominal speed because Johnson is such a strong man.
Bloody hell! I had no idea that there was this spiritual quality of ‘strength’ that can attach to a ball, quite independently of its velocity. Does the delivery of each ball diminish Johnson’s stock of ‘strength’? Does it come back in time if Johnson rests? Can he transfer this strength to objects other than cricket balls? Can he, perhaps, lay his hands upon someone suffering extreme ennui and thereby restore their zest for life?
Back to reality: I do hope that this commentator doesn’t coach bowling. How hard a ball hits a bat depends upon the ball’s mass and velocity at the time it strikes the bat (I’m assuming friction between the bat and ball is fairly low). The only way, for a given speed of delivery, for a ball to strike in a more ‘heavy’ manner is for Johnson to substitute another, heavier, ball, thereby increasing both the momentum (=MV) and kinetic energy (=0.5MV^2) of the ball, or for him to employ some trick. Since the former is cheating, I shall assume the latter.
A large portion of the delivery speed is washed off between the time when the ball leaves the bowler’s hand, and when it arrives at the batsman’s crease. Some of this is from air friction, but the bulk is lost when the ball hits the pitch. If Johnson is able to impart some top spin to the ball during his high speed delivery, this could reduce the amount of speed lost.
Another possibility is that this is simply in some cricketers’, or cricket commentators’, imaginations.
It’s a bit like that with home entertainment stuff. Some listeners decry technical or ‘reductionist’ explanations of how well (or otherwise) these things perform. Some suggest that the human ear is the most sensitive instrument. Which is silly, because the ear isn’t an instrument at all. It is a bodgey tool developed by evolution to do a specific job which has nothing at all to do with measurement. It is intended to provide enough information to allow our equally bodgey audio processing circuits to generate a tolerably accurate aural picture of the world around us. Most importantly, to do this at high speed. Having a higher accuracy picture isn’t much use if during the time it takes for all the processing to be completed the cheetah that was creating the sound has raced up and bitten off our heads.
If you can hear or see differences between two pieces of equipment that their specification sheets don’t seem to suggest, that doesn’t mean that they won’t measure differently. Measure the right things with technical equipment, sufficiently finely, and in the right conditions, and you can define every discernible aspect of its performance.
But it may still sound different to different people from time to time because we also have imaginations, hormones, moods.