Cali Balances the Seesaw – Lever Game

Put bricks, people and mystery objects on a seesaw and find out when it balances. In 4 levels of 6 challenges Cali asks you where to put an object, what the mass of an unknown object is and what will happen when the supports are removed. Your best stars are saved in this browser.

How to play

Placing objects: drag the object from the shelf to a mark on the seesaw, or tap it and then tap the mark. An object you placed can be moved in the same way; objects with a lock stay where they are.
Levels 1 and 2: put the bricks or the person on the right side so that the seesaw balances, then press Check: the supports go away and you see what happens.
Level 3: balance the mystery object with bricks (at most 4 on one mark). Remove the supports and put them back as often as you like to test. Then type the mass of the object and press Check.
Level 4: nothing can be moved here. Say what the seesaw will do when the supports are removed; only your first answer counts.
Points and stars: a right answer on the first try gives 2 points, on the second try 1 point. After two wrong tries “Show me” shows the answer. 11 or 12 points earn 3 stars, 8 to 10 points earn 2 stars. Every level is open from the start.
Arrows: this switch draws an arrow under each object; the heavier the object, the longer its arrow.
Keyboard: press Tab to reach the object on the shelf and Enter to pick it up, choose a mark with the Left and Right arrow keys and press Enter again. Delete sends an object back to the shelf, S removes and puts back the supports in level 3, the keys 1, 2 and 3 choose the answer in level 4, Ctrl+Z undoes the last move and Esc goes back to the levels.
Units: the game measures in pounds and feet: one brick is 10 lb and the marks are 1 ft apart.

What the game teaches

The lever. A seesaw is a lever. It balances when mass × distance from the pivot is the same on both sides. A 40 lb child 6 ft from the pivot balances a 60 lb child 4 ft away, because 40 × 6 = 60 × 4 = 240.

Light can balance heavy. That is why a light object far from the pivot can balance a heavy one close to it, and how a balance can measure an unknown mass.

In physics the weight of each object is a force F = m · g, and mass × distance becomes the moment of the force, F · d.