Photo Shows the Demonstration Used by the University of Texas at Austin.

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 reference point.

• 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 returns to.

• 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 - All Rights Reserved.