Solve Pendulum Problem: Tension 150 N, Mass .65 kg, 28m Apart

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The problem involves a cord with a mass of 0.65 kg stretched between two supports 28 m apart, with a tension of 150 N. To determine the time it takes for a pulse to travel along the cord, the correct wave speed formula is v = √(F/(m/L)). Using this formula, the wave speed is calculated to be approximately 80.35 m/s. Consequently, the time for the pulse to travel the length of the cord is found to be 0.35 seconds. The initial confusion stemmed from incorrectly applying pendulum equations instead of focusing on the wave properties of the stretched cord.
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Homework Statement


A cord of mass .65 kg is stretched between two supports 28 m apart. If the tension in the cord is 150 N, how long will it take a pulse to travel from one support to the other?


Homework Equations


umm... the only equation to find helpful was...

T = 2pi\sqrt{m/(mg/L)} = 2pi\sqrt{m/(F/L)}?


The Attempt at a Solution



Knowns:

F (tension) = 150 N
m = .65 kg
L = 28 m

2pi\sqrt{.65 kg/(150 N/28 m)} = 2.19 s?

Though the book says it is 35 s...

Help? Should there be another equation that I should be using or did I miss something?
 
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Hi Kandycat,

Kandycat said:

Homework Statement


A cord of mass .65 kg is stretched between two supports 28 m apart. If the tension in the cord is 150 N, how long will it take a pulse to travel from one support to the other?


Homework Equations


umm... the only equation to find helpful was...

T = 2pi\sqrt{m/(mg/L)} = 2pi\sqrt{m/(F/L)}?

This is not a pendulum, so these equations do not apply here. In this problem, a cord is stretched and a pulse is made to travel along the cord, so you want to find an expression for the wave speed of a stretched string. What would that be?
 
Oh... so is it v = \sqrt{F(t)/(m/L)}?

v = \sqrt{150 N/(.65 kg/ 28 m)} = 80.35 m/s

T = L/v = 28 m/80.35 m/s = .35 s

Thanks!

Sorry about that.
 
That looks right to me!
 
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