B2-41: ROBERVAL BALANCE

ID Code: B2-41
Purpose: Demonstrate a paradox in equilibrium of forces and torques
Description: This unlikely-looking contraption is in neutral equilibrium when equal weights are placed onto the two outer arms, as shown, so it will remain at rest in any position. If a net weight is placed on either side, that side will go down.
Ask your students what they think will happen when the system is released in the configuration photographed at the left above. Draw attention to the similarity between the Roberval balance and the simple pan balance.
Availability: Available