Problem 12
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
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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?