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Problem 12 Wet towels. Overview. 1. 2. 3. Pros. 1. 2. 3. 4. 5. 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
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Overview • 1. • 2. • 3.
Pros • 1. • 2. • 3. • 4. • 5.
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 • 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?