Our sense of hearing interprets the changes in frequencies as a change in pitch. A more secure object may vibrate faster than a loose object when struck. As the glass is filled, it becomes more stable and vibrates slower when struck. Action Divide students into groups and assign each group to one shape of cup. Fill cups with water to different levels.
Students tap the rim of each cup with a pencil.
After they've tapped the rims several times, ask students why they think there is a difference. Student groups may hear different pitches for different shaped cups filled to the same level of water. Tall glasses may vibrate faster than short, wide glasses. Students can also determine what notes each glass produces by comparing sounds with a known musical instrument. Inc. All Rights Reserved.