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Description: This demonstration illustrates driven resonance of a mass on a spring with the option of damping.
Equipment:
- Texas Towers apparatus
- Mechanical motor
- Spring
- Bob
- Glass tank
Setup Procedure:
- Clamp the Texas Towers apparatus to a table.
- Connect the string to the motor.
- Hang the string over the two pulleys.
- Connect the spring to the other side of the string. Connect the bob (mass) to the end of the spring.
- Fill the tank with water.
- Test to make sure all equipment is working.
- When the teacher is finished, to not take apart the Texas Towers apparatus. Leave it as one unit and return to where you got it.
Demonstration Procedure:
- Explain to students that you have a mass on a spring, which is driven by a motor.
- Turn on the motor and show what happens to the spring when you change the frequency.
- Find the frequency where there is very little amplitude.
- Find the resonant frequency and note how high the bob goes (very high).
- Turn off the motor and position the tank of water under the bob so that the bob does not touch the glass.
- This shows the effects of damping on a driven oscillator. Before the damping the bob and spring were in turned to resonance. With the water damping though, the resonant frequency changed.
- Adjust the frequency again to find the new resonant frequency.
- When finished, turn off the motor and take the bob out of the water.
Note: Do not make adjustments to the top of the apparatus.