Propositions on percussion: bells, nails, and falling weights
Why jerked force beats steady force; why a dropped weight makes water leap up
This densely packed page assembles some fifteen questions and observations on percussion and motion. Leonardo asks why a jerked pull or push is more powerful than steady force, why a struck bell keeps ringing, and how a nail waxed to the hammer drives home in a single blow. He notes acoustic effects, the report of a bombard, a burst bladder, a child's elderwood popgun, as air violently released, and observes that a weight dropped into water makes the displaced water leap upward where it meets least resistance. He also distinguishes 'accidental' upward motion from 'natural' descent, and explains that a slung stone flies off only because of the jerk of release.
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Jerked force is stronger than steady force
Leonardo asks why pulling and pushing in jerks is more powerful than continuous force, and why a struck bell keeps sounding after the blow. He observes that a short vigorous motion can equal a long weak one, as a cherry-stone squeezed between two fingers flies as far as one thrown by hand.
A nail waxed to the hammer drives in one blow
Driving a nail by many separate blows is slow and difficult; but if you fasten the nail to the hammer with wax, a single blow will drive it wholly into the board. Fix a nail's point slightly and strike the board hard from the far side, and the nail will pass through to meet the hammer.
The report of bombard, bladder, and popgun
Air forced and shut into a place makes a report when it escapes and strikes the outer air, as seen in bombards, in a burst bladder, in the popguns children make by driving berries into an elder tube, and in deflating a ball or bellows.
Water leaps up where a weight falls in
A weight falling into water enters so swiftly that the surrounding water, held up by the rest, cannot give it room and must flee where it finds least resistance. Since air resists less than water, the displaced water leaps up toward the air.
