OBJECT: To study the manner in which the deflection of a beam depends upon its length, and to determine Young’s modulus by the method of flexure.
METHOD: A uniform rectangular bar supported horizontally on two knife-edges is subjected to a vertical force applied midway between the supports. The deflection of the beam at the midpoint is measured by means of a micrometer screw equipped with an electrical contact. A series of observations is made with a constant load and a varying length of beam (distance between supports). From a logarithmic graph of the deflection versus the length, the mathematical relationship between deflection and length is ascertained. A second series of observations is made in which the load is varied, the length remaining constant. From the slope of a graph of load versus deflection, a value for Young’s modulus is obtained.
