# Lowest frequency of a water with drinking straw

## Homework Statement

the ans given here is 'using the opened pipe method'. but i solve it using closed pipe method. which i have sketched using the pencil on the right of the diagram. why cant i solve it using 'closed pipe method' , i just couldnt understand.

## The Attempt at a Solution

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CWatters
Homework Helper
Gold Member
A straw is open both ends. It would only be closed one end when you put it into the drink. That is not stated in the problem. How do you know how far the straw is inserted into the drink? If that information was provided you could work it out by treating one end open and the other closed.

CWatters
Homework Helper
Gold Member
PS Do you understand why you get a node at a closed end and an antinode at an open end?

The air will vibrate at open end so it is antinode. The air wouldnt vibrate at closed end so it is node.

BruceW
Homework Helper

## Homework Statement

the ans given here is 'using the opened pipe method'. but i solve it using closed pipe method. which i have sketched using the pencil on the right of the diagram. why cant i solve it using 'closed pipe method' , i just couldnt understand.
This is a good point. It is hard to tell if the straw is closed at one end, or open at both ends. This website http://www.phys.unsw.edu.au/jw/flutes.v.clarinets.html might help a bit. But anyway, to find out I guess you could physically try to get a sound wave to go through a straw. If your mouth is fully closed around the straw, then it is closed at one end. But if you can only make the vibrations when you don't have a tight seal around the straw, then it is open at both ends.

CWatters
Homework Helper
Gold Member
Problem says "blows at the end". I guess not 100% clear but I would take that to mean blow across the end from a distance like you would a bottle.

CWatters