PIRA 1R20.15 - Tensile and Comprehensive Stress: Young's Modulus
Photo Shows the Demonstration Used by the University of Texas
Instructions and Notes:
- A solid steel wire is wrapped around a rotating axle that has a mirror
attached to it.
- A laser beam shines into the mirror and is reflected back towards a
- At the bottom of the wire is a 1 kg hanger to which additional kilogram masses can be added.
- The axle rotates as the wire is stretched downward when additional 1 kg masses are added to the hanger which changes angle of the mirror.
- The reflected laser beam shows progressive movement as a series of
masses are added to the hanger, causing the wire to stretch.
- A series of 1 kg masses can be added one at a time to the hanger.
- 2 kg masses are available for this demonstration.
- Have students note the degree of movement after each weight is added
to the hanger.
- As you remove the masses students can observe where the reflected beam
- Limit the total mass on the hanger to no more than 5 kilograms to avoid
breaking the wire.
Last Updated 3/98 - University of Texas at Austin Physics Department
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