Young’s Modulus Experiment

A central experiment in the Modern Mechanics semester is a measurement of Young’s modulus, from which we extract by a macro-micro analysis the effective stiffness of the interatomic bond, modeled as a spring in the ball-and-spring model of solids. The goal of the experiment is not to get a high-precision measurement of Young’s modulus but rather to give students a feeling for the nature of the phenomenon and the size of the effects. A home-built apparatus for this is shown below. A wire nearly 2 meters long goes from the bottom of the upright frame over two pulleys and down to a slider that passes through a slot marked in millimeters. Accuracy is limited more by the difficulty to eliminate all kinks in the long wire than by how well the stretch can be measured, so for directness and simplicity we don’t have a Vernier scale (whose use would have to be explained). The base comes off so that the base and upright frame stack for compact storage.  The frame is made of hollow square aluminum tubing.

Measurements and drawings for constructing the apparatus, and additional detailed photos.

If appropriate equipment is not available, consider having students obtain data to analyze from this video: https://youtu.be/XS-lVAyvySk

E&M Desktop Experiment Kit

A student desktop experiment kit to accompany Volume 2 on electricity and magnetism is available from PASCO: search for item EM-8675. With the kit students can do experiments with electrostatics, circuits, and magnetism. The kit contains

a roll of invisible tape (which charges well for electrostatics experiments)
batteries
a battery holder
a bar magnet
a liquid-filled compass
high and low resistance light bulbs
bulb sockets
a 1-farad capacitor
thick and thin Nichrome wires
clip leads
a long wire
recent additions are a 47-ohm resistor and a 100-ohm resistor
If you choose to assemble your own kits (which is more difficult than you might imagine), here is useful procurement information.