10 Oscillations

Box on a Vertical Oscillating Spring – Geogebra App


GeoGebra link: https://www.geogebra.org/m/ev62ku7w

Students can explore how varying frequency and amplitude of the vertical oscillation of a platform could cause an object resting on it to temporarily leave the platform (i.e. when normal contact force is zero).

Velocity-Displacement Graph of a Simple Harmonic Oscillator – Animation

This animation is made using Geogebra. It shows the instantaneous velocity and displacement vectors of a particle undergoing simple harmonic motion while tracing its position on the velocity-displacement graph. It is meant to help student understand why the graph is an ellipse.

LEGO Pendulum Clock to Demonstrate Oscillation Concepts

This is the Pendulum Clock from the LEGO Education Simple and Powered Machines Set. It can be used to demonstrate the variation of period with length of pendulum and is a very good visual representation of the escapement mechanism.

There are many other models that one can build using this set, including a weighing scale, elastic energy powered car, etc. All with potential for class demonstrations.

You can buy a set from Duck Learning in Singapore at (S$329.75), an exclusive distributor of LEGO Education products in Singapore. If you are purchasing in bulk for your school, you may want to contact them directly for a package deal. You can also purchase them from overseas sites such as Bricklink.com if you can find them at a better price.

Tacoma Narrows Bridge

This is a video that we usually will show during a lecture on the topic of Resonance, under the unit “Oscillations”.  It was taken in 1940 at the Tacoma Narrows Bridge in Washington, USA. One of the main reasons (not the only reason – the other being aeroelastic flutter) for its collapse is the effect of resonance, which occurs when the driving frequency of the wind that hits the bridge matches the natural frequency of vibration of the bridge.

Tuning a Guitar using Resonance

There are many ways to tune a guitar. Many musicians would have tuned a string instrument using a tuning fork at some point. However, the conventional method of tuning with a tuning fork is by listening to beats while adjusting the tension of the string. The tuning fork is of a known frequency which corresponds to a note. For instance, 440 Hz corresponds to an A-note. When the A-note string is slightly out of tune, such as having a frequency of 438 Hz, the resulting sound pattern (called beats) will have a frequency that is the difference between the two frequencies, i.e. 2 Hz. Hence, the aim of tuning by listening to beats is to adjust the tension of the string until the beats disappear.

An alternative method, which is the one we shall attempt in this demonstration, is to run the vibrating tuning fork along the E-string (this first from the top) until you reach the bridge between the 5th and 6th frets. You should expect to hear a loud resonating sound there. Otherwise, adjust the tension until you do.

All the other strings are tuned with respect to that first string.

Explanation

Resonance is the phenomenon where the frequency of the tuning fork (driving frequency) is equal to the frequency of the string (natural frequency) and maximum energy is transferred from the tuning fork to the string. The string will hence oscillate with the maximum amplitude.