Match on water sustained by surface tension

AI Thread Summary
When soap is added to one side of a match floating on water, the match moves towards the side with pure water due to the difference in surface tension between the soap and water. The force acting on the match is calculated using the formula F = (sigma water - sigma soap) * l, where sigma represents surface tension. The higher surface tension of water compared to soap creates an imbalance, propelling the match towards the water. This movement occurs because the soap reduces the surface tension on one side, allowing the greater tension on the opposite side to exert a force. Understanding this phenomenon involves recognizing the role of surface tension in fluid dynamics.
RingNebula57
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Homework Statement


A match of length l=4cm is floating on the surface of the water from a glass. ( the water is at room temperature) If from on one side of the match we pour a few drops of soap, the match starts moving. In which direction is the match mooving and what force is acting upon it? ( sigma (water) = 73 mN/m ; sigma (soap) = 43 mN/m)

Homework Equations


F= sigma * l

The Attempt at a Solution


The force acting on the match is F= (sigma water - sigma soap) * l. I don't fully uderstand how the phenomenon is going on ... could someone draw what's happening in this problem ?

thank you!
 
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RingNebula57 said:
which direction is the match mooving
 
towards the pure water
 
What causes that?
 
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