Balancing a seesaw – moments on a plank with a central pivot

Integrated ScienceForces & MotionAges 13–14

Place bricks, people and mystery objects on either side of a 4 m seesaw with the pivot in the middle and positions 0.25 m apart. The plank balances when the total moment m·g·x on each side is equal; remove the supports to watch the plank turn under the resultant moment, slow down and stop when level or touching the ground. Three screens: Intro (stacked bricks), Lab (a shelf of objects plus 6 mystery objects to balance and find their mass) and Game (4 levels, 3 types of challenge). Adapted from the "Balancing Act" simulation by PhET Interactive Simulations, University of Colorado Boulder (CC BY 4.0); rewritten.

Lesson: Moments; levers and their uses