Seesaw Balance

This simulation shows the law of the lever on a 10 meter plank. Students drag each block to a new spot, snapping to half-meter marks, and click a block to make it heavier. The plank tilts in proportion to the net torque, and readouts compare left and right torque so learners can see when they are equal. Teachers can pose balancing challenges, such as making a 2 kg block balance a 1 kg block, then ask students to explain the mass times distance rule. Sliders adjust the maximum tilt and turn snapping on or off.

• Drag one block to the far left end and another to the right until the Plank readout says it is level.
• Click a block to make it heavier, then move it closer to the pivot to restore balance.
• Compare the Left torque and Right torque readouts while you slide a block half a meter at a time.
• Turn off Snap to marks and try to balance the plank at an in-between position.
• Raise Max tilt to 30 degrees to see how strongly an unbalanced plank swings.

1. 1State that a lever balances when mass times distance is equal on both sides.
2. 2Predict where to place a heavier block so the plank stays level.
3. 3Explain why doubling a mass allows its distance to be halved.
4. 4Use torque readouts as evidence to check a balancing prediction.

Questions teachers ask