Solving Physics Homework: Frequency Change

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Homework Help Overview

The problem involves a vibrating cord with a specified frequency when a certain mass is applied. The original poster attempts to determine the new frequency when a different mass is used, referencing a specific formula related to oscillation frequency and mass.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the relationship between mass and frequency, with some suggesting a ratio approach based on the masses involved. Questions arise regarding the nature of the motion (oscillating mass versus vibrating cord) and the appropriateness of the formula used.

Discussion Status

There is an ongoing exploration of the problem, with participants questioning the assumptions made about the type of motion and the applicability of the formula. Some guidance is offered regarding the use of ratios, but there is no explicit consensus on the correct approach or interpretation of the problem.

Contextual Notes

Participants note potential confusion regarding the textbook's instructions and the implications of using different units for mass. The distinction between types of motion is also highlighted as a critical factor in understanding the problem.

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Homework Statement


A cord vibrates with a frequency of 3.0 Hz when a mass of 0.60kg is hung up from it. What is its frequency if only 0.38kg hangs from it?

Homework Equations



f= 1/2pi sqrt k/m

The Attempt at a Solution


3.0= 1/2pi sqrt ( k/0.6)
k=213.18 N/m

f= 1/2pi sqrt (213.18/ 0.38)
f= 37.2 Hz[/B]
 
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The ratio between the masses is 60:38, so the ratio of frequencies is the square root of that.

But what is this about: an oscillating mass on an elastic string or a vibrating cord under tension?
 
@PietKuip it just says an elastic cord vibrates when a mass is hung from it. Also, what is wrong in my calculations is it that you are supposed to use grams for the mass?
 
Actually it can't be because I used kg that is what you are supposed to use.
 
Units don't matter, just use the ratio.

It is quite a difference if the mass is oscillating up and down on a string or whether the string is in a transverse oscillation without the mass moving. Different kinds of motion, different formulas apply.
 
@PietKuip I understand that the ratio method will work. But I am a bit concerned why what I did above did not work as my textbook specifically said to use that formula.
 
Weird textbook. How can one learn any physics that way? The wording suggests a different mode of motion than for the case where this formula applies.
 

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