To set up and use the Standing Waves experiment:
Step 1: String Vibrator
Use a table clamp to attach the string vibrator to the edge of a table.
Use a block of wood as a spacer so that the vibrator doesn't touch the table top.
Step 2: Pulley
Use a pulley clamp to attach a pulley to the other side of the
table. Note that if you attach the vibrator and pulley across a corner (instead of across the whole table as I did), you can adjust the length of the string by moving the pulley or vibrator.
Step 3: Mass Hanger
Hang a mass hanger on the free end of the string.
Step 4: Length
Measure the length L of the vibrating part of the string; that is, between the top of the pulley and the end of the vibrator's tongue.
Step 5: Power
Plug in the vibrator. These have a fixed frequency f = 120 Hz.
Step 6: Make Standing Waves
Add mass to the hanger until a standing wave forms. Record the hanging mass M and the number of antinodes n. Don't forget that the hanger is 50 g.
Step 7: Mass Per Unit Length
Get a long piece of string and measure its length. (The piece in the picture is 2 m long.) Use the electronic scale to find its mass. From these you can calculate the mass per unit length.
Note, however, that the string stretches when under tension, so that the mass per unit length of the vibrating string is less than that of the unstretched string. If you measure how far the string stretches, you can use this to adjust the mass per unit length.