Have you ever gone past a construction site or driven over a bridge and noticed that the supporting beams in a structure can be designed with a variety of cross-sectional shapes? In this activity, you will explore how changing the cross section of a beam affects the amount of deflection (or “bendiness”) a beam exhibits under a load. Your goal is to develop a model that will allow you to predict the relative deflection of a center-loaded beam supported on both ends based on its cross section shape.


  • Students will engage in an inquiry activity to develop a model based on observations (of their own devising) from the physical world.
  • Students will understand the factors that affect the deflection of a center-loaded beam, supported on both ends, with identical volume and mass of material, but with varied cross-sections.
  • Students will construct a model representing the relationship of the factors related to cross-section shape affecting the deflection of center-loaded beams.