M-S 5: Equilibrium of forces acting on an extended body

PIRA: Unknown

Equipment: two platform scales, two triangular prisms of wood made by sawing a square molding along its diagonal, large cylindrical slotted weight about 5 kg, wooden plank. The board is on top of Set 8, Cabinet 1 and the balances are in Set 11, Cabinet 3, Shelf 1.

Procedure: Set up the situation shown in the photo with the wooden prisms having their 90 edges projecting upward so simulate the supports at each pier. Adjust with the heavy weight off the plank until the scales read the same. Then the weight may be placed at any point on the plank or slowly rolled from one end of the "bridge" to the other, showing how the weight is divided between the "piers."

The large circular discs that appear on the table near each scale are covers for the face of the scales in case the demonstrator wants to collect student opinion before revealing the results.