(I’m talking about the motion of flicking an insect off your arm, where you rest your finger against your thumb and release it.) What is it about using the thumb that gives so much more power to the motion of your finger? You would think that scraping your finger against something would slow down the motion, or make it less powerful.
You ever opened a bag of potato chips? I have. You ever opened a bag of potato chips, only to have the bag split down the middle, chips flying across the room? I have. I’m always very careful when I open a bag of potato chips. Being the virile man that I am, I possess the strength to open ten, possibly twenty, bags of potato chips. However, initially I humbly approach the bag with weakness, slowly mustering (just!) enough strength split the seam of the top of the bag, while allowing the rest of the bag to maintain its integrity.
My hypothesis is that this finger flicking of which you speak is a very similar process. Admittedly, I do not have any scientific instuments with which to measure my experiments, but sitting here at the computer, I believe that I can accelerate the tip of my Finger of Doom (FOD), to insect propelling velocity (IPV) with or without the thumb propellant (TP).
I believe what is happening is more psychological (and admittedly satisfying) than any mere physical property. By utilizing TP, a (relatively) considerable force is initially required to provide any acceleration whatsoever to FOD, insuring that once FOD leaves the thumb base, virtually instantaneous IPV is assured.
As I previously said, I believe that my FOD can achieve IPV without TP. I simply will the FOD to move as quickly and instantaneously as possible. However, TP provides a simple means of guaranteeing the proper velocity is achieved (and, as mentioned, is somewhat psychologically satisfying), much as the initial resistance of said potato chip bag insures that I will be applying some minimal (but positive!) amount of force once the potato chip bag succumbs to my superior strength.
Comments on my research are welcome.
Your thumb is your strongest finger. What it’s doing is holding your flicking finger back and then suddenly releasing it. Your finger has been pushing hard on your thumb and when your thumb lets go your finger going flying.
You’re basically using your finger as a spring.
As you have your finger pressed against your thumb, you contract the muscles on the top of your finger. Your tendons will stretch a little, your muscles will be tensed, trying to fulfill your brain’s command to contract. When you move your thumb out of the way, your finger muscles and tendons will contract suddenly with the end result being your finger tip moving at insect-crushing speed. If you didn’t use your thumb, your finger would only move as fast as your various muscle fibers could obey your brain’s command. With your thumb, all of your muscles are already contracted or contracting, giving you more force.
I used to play this stupid game in middle school - I would hold both ends of a pencil, and my friend would try to break it with his. He would hold one end with his hand, and bend the other one back, straining boths sides. The best pencils for this would bend a little, so the combined forces of his straining hand muscles and the bent pencil would cause his pencil tip to smack down on mine with a suprising amount of force. The force generated was a lot higher than what you could get form just smacking the pencil down.
Three interesting replies. Thanks, guys.
I’m going to guess that you can’t bring your finger muscles directly from “all-off” to “all-on” instantly. It takes a little time to get up to full force. On a free (no thumb) flick, your finger reaches maximum extension before you reach full force, but with the thumb, you can take as much time as you want to build up force.
Yeah, you can take as much time as you want – but you (or at least I) don’t. I thinkwhat Tower Dweller said about muscle contraction makes sense. Try a “free flick” and then a “thumb flick” against your own arm – clearly the “free flick” has significantly less force behind it, even if you take your time.