Match on water sustained by surface tension

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Homework Help Overview

The problem involves a match floating on the surface of water and the effects of soap on surface tension. Participants are exploring how the introduction of soap alters the forces acting on the match and its resulting motion.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to calculate the force acting on the match based on the difference in surface tension between water and soap. Some participants question the direction of the match's movement and the underlying causes of this movement.

Discussion Status

The discussion is active, with participants providing insights into the direction of the match's movement and prompting further inquiry into the reasons behind this behavior. There is an exploration of the effects of surface tension changes due to soap.

Contextual Notes

Participants are considering the implications of surface tension values provided for both water and soap, as well as the physical setup of the match floating on the water's surface.

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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