Problem 12 Wet towels Overview 1 2 3
Problem 12 Wet towels
Overview • 1. • 2. • 3.
Cons • • 1. 2. 3. 4.
Problem • When a wet towel is flicked, it may create a cracking sound like a whip. Investigate the effect. Why does a wet towel crack louder than a dry one?
Direction of discussion • • 1. Definition 2. Experiment 3. Parameters 4. Sound
Question on definitions • 1. How do you define the “cracking ” sound • 2. How do you distinguish the “cracking” sound from other sound? From frequency or from energy?
Question on experiment
Question on experiment • 1. Is your frame rate fast enough to capture the fastest moment ? Then how long would the moment last? • 2. How do you control the distance between the towels and recorder? • 3. If you put a ruler and capture it from a distance, would there be some deformation?
Questions on parameters • 1. How do you control the force when whipping towels with different weight? • 2. Do you take the weight difference before and after whipped into consideration? • 3. Is there some water be whipped out from the towel ? Will it affect the result? • 4. In which circumstances will you stop adding water to the towel?
Questions on parameters • 5. Is there any different at the end of the towel after whipped? How do you control this part • 6. Will the way of whipping a towel affect the sound? • 7. Will air resistance affect the towel greatly? • 8. A wet towel or a dry towel have greater rate of energy transformation than a dry towel? Why?
Sound • 1. What is the origin of the ”Cracking” sound ? • 2. Which parameter do you think contribute the most to the lager cracking sound of wet towel? • 3. Do you think the shape of the towel end will affect the sound?
Questions for Data • 1. How many times do you whip a towel for one data point? • 2. Is your experiment repeatable?
- Slides: 13