Solving Physics Homework: Frequency Change

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SUMMARY

The discussion centers on calculating the frequency change of a vibrating cord when different masses are applied. Initially, a mass of 0.60 kg results in a frequency of 3.0 Hz, while a mass of 0.38 kg yields a frequency of 37.2 Hz using the formula f = 1/2π √(k/m). The spring constant k was determined to be 213.18 N/m. Participants highlighted the importance of understanding the type of oscillation involved, as different modes of motion require different formulas, leading to confusion regarding the textbook's instructions.

PREREQUISITES
  • Understanding of harmonic motion and oscillation principles
  • Familiarity with the formula f = 1/2π √(k/m)
  • Knowledge of spring constants and their calculation
  • Basic grasp of mass and frequency relationships in physics
NEXT STEPS
  • Study the differences between longitudinal and transverse waves in oscillating systems
  • Learn about the implications of mass ratios on frequency changes in vibrating systems
  • Explore the derivation and applications of the formula f = 1/2π √(k/m)
  • Investigate common misconceptions in physics textbooks regarding oscillation types
USEFUL FOR

Students studying physics, educators teaching harmonic motion, and anyone interested in understanding the dynamics of vibrating systems and their frequency calculations.

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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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