- #1
Soren4
- 128
- 2
Homework Statement
A rope has an end fixed and the other is passing through a pulley and has a body attached to it. The fondamental frequency of the rope is initially ##f_1=400 Hz##. If the body is then put in water the fondamental frequency of the rope becomes ##f_2=345 Hz##. If the linear mass density of the rope is ##\mu=10 g/m## determine
a) the density ##\rho## of the body
b) the length of the horizontal part of the rope ##L##
Homework Equations
The Attempt at a Solution
For point a) I don't have problems since
$$\frac{f_2}{f_1}=\sqrt{\frac{T_1}{T_2}}=\sqrt{\frac{mg-\rho_{H_2O}Vg}{mg}}=\sqrt{\frac{mg-\rho_{H_2O}\frac{m}{\rho}g}{mg}}=\sqrt{1-\frac{\rho_{H_2 O}}{\rho}}$$
Where ##T## is the tension of the rope. From which I can get ##\rho##
But what about point b)?! It seems impossible to me to get ##L## just knowing ##\rho##, ##f_1##, ##f_2## and ##\mu##..
These conditions are not enough, how can I determine ##L##?