Ruler leverage / balance toy learning kit
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Turn a school ruler and a pencil into a balance beam, plus six solids that all hold exactly 8 cm3.
- Ocena
- 0 / 5
- Polubienia
- 6
- Pobrania
- 0
- Wydruki
- 0
- Wyświetlenia
- 20
- Oceny
- 0
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Informacje o modelu
- Źródło
- Printables
- Kategoria
- Other Toys & Games
- Licencja
- Creative Commons — Attribution
I made this for a maths lesson on levers and it ended up covering two.
It's one block with a slot through it. Push a school ruler through and you have a lever, and because the ruler isn't clamped it slides, so the pivot goes wherever you want. That's the good bit: the beam measures itself. Both arm lengths come straight off the ruler's own scale, and you can change them mid-sentence while everyone watches.
Three ways to stand it up
Two feet on one side of the slot, a rounded dome on the other.
Dome down it rocks, and tips hard the moment one side wins. That's the one for "which is heavier", and the one that gets a reaction. Feet down there's no pivot at all and the ruler just sits horizontal.
Pencil through the hole is the calm version. Hold both ends, or lay it across two stacks of books. The ruler ends up about 15 mm under the pivot, so it settles instead of slamming. Move a weight a centimetre and it leans about 10 degrees and stays there, so you can talk about how much heavier, not just which side.
Either way it's weight times distance on both sides, and they get there by shoving things around instead of copying a formula.
The shapes are optional
Coins work fine. If you print them, all seven hold 8 cm3, the same as the 20 mm
cube: cube, two cylinders, cone, hemisphere, pyramid, prism. Any two at the same distance sit level. The cone is half again as tall as the cube and still balances it, and the hemisphere looks far too small and balances too. Get them to guess first.
Print the shapes at 100 % infill. Equal volume only means equal weight if they're solid through. A cone has much more surface per cm3 than a cube, so at normal infill the shell does the weighing and the masses drift about 3 % apart, which is a couple of degrees of lean on something meant to sit level.
The block is a normal print. PLA, 0.2 mm, flat on the bed, no supports.
Running it
Dome down, pivot in the middle, one weight on the left: it drops. Same weight on the right at the same distance: level. Slide the block off centre, read the arms off the ruler and ask what they'd do before you tell them. Then the pencil, where the lean is proportional. Cube against cone last, vote first.
Slot 3.0 x 42 mm for a flat school ruler, hole 11 mm for a pencil, block 35 x 50 x 31 mm.