Problem 12Problem 12
Wet towels Wet towels
Overview
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Pros
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Cons
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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?
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