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## Homework Statement

A hanging cord is attached to a fixed support at the top and is 78.0m long. It is stretched taut by a weight with mass 21.0kg attached at the lower end. The mass of the cord is 2.20kg . A device at the bottom oscillates the cord by tapping it sideways (Do

*not*neglect the weight of the cord.)

1.) What is the wave speed at the bottom of the cord?

2.)What is the wave speed at the middle of the cord?

3.)What is the wave speed at the top of the cord?

## Homework Equations

[itex]v = \sqrt{T/µ} [/itex]

where [itex]T[/itex] is the tension force on the string and [itex]µ[/itex] is the mass per unit length.

## The Attempt at a Solution

After reading my text and browsing the forums for help it seems that the tension of a cord with non-negligible mass in this case is [itex]T = µ(m1 + m2)L[/itex] where [itex]m1[/itex] is the mass of the ball and [itex]m2[/itex] is the mass of the cord.

[itex]T = \sqrt{µ(m1 + m2)*L/µ} = \sqrt{(m1 + m2)*L}[/itex]

Plugging in I obtain [itex]42.5 m/s[/itex]

Which seems to suggest that the speed is the same at every point. However I'm having serious doubts about the answer I've reached. Is that true? Or am I missing something very important here?