Length of Pendulum Homework: Find String Length

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Homework Help Overview

The problem involves calculating the length of a pendulum string based on the mass of the bob, the angle of release, and the time taken for multiple oscillations. The subject area is related to oscillatory motion and pendulum dynamics.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the use of the formula for the period of a pendulum and question the accuracy of their calculations. There is an exploration of the relationship between period and frequency, as well as the implications of using different values for gravitational acceleration.

Discussion Status

Some participants have provided feedback on calculations and suggested checking assumptions about gravitational acceleration. There appears to be a productive exchange regarding the understanding of period and frequency, with one participant indicating a realization of a mistake in their approach.

Contextual Notes

There is mention of a discrepancy with the answer provided by MasteringPhysics, indicating possible constraints or specific expectations from the homework platform.

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Homework Statement



A 319g ball is tied to a string. It is pulled to an angle of 7.60 degrees and released to swing as a pendulum. A student with a stopwatch finds that 14 oscillations take 13.0s.
What is the length of the string?

Homework Equations


I have already tried using T = 2pi sqrtL/g, but that does not give me the right answer.


The Attempt at a Solution

 
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Show your work so we can see what you did.
 
13 oscillations/14 seconds = 1.07 for T, and 1/1.07 = 0.928s for f.
Then I tried T = 2pi sqrt L/g, so 1.07 = 6.28 sqrt L/9.8m/s, then divided each side by 6.28 and got 0.170 = sqrt L/9.8, then squared each side, so 0.029 = L/9.8, then solve for L = 0.2842m, which is wrong according to MasteringPhysics.
 
How far off is your answer?

It looks okay to me. Is the g value for Earth or some other planet?
 
Last edited:
I figured it out...I had period and frequency backwards
 

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