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Mechanical Properties Of Fluids

Question
CBSEENPH11018729

Find the velocity of wave in a string of linear mass density m when stretched to tension T?

Solution
Let velocity of wave in the string vary with ath power of m and bth power of T.
That is, 
                 straight v proportional to straight m to the power of straight a

space space space proportional to straight T to the power of straight b
space space space 
∴            straight v proportional to straight m to the power of straight a straight T to the power of straight b 
rightwards double arrow      space space space space space straight v equals straight k space straight m to the power of straight a space straight T to the power of straight b          ...(1)
where,
k is constant of proportionality.
If this relation is true then dimensions of each term on both sides will be same.
Substituting the dimension formula of each quantity in equation (1),
          left square bracket straight M to the power of 0 straight L to the power of 1 straight T to the power of negative 1 end exponent right square bracket space equals space left square bracket straight M to the power of 1 straight L to the power of negative 1 end exponent straight T to the power of 0 right square bracket to the power of straight a space open square brackets straight M to the power of 1 straight L to the power of 1 straight T to the power of negative 2 end exponent close square brackets to the power of straight b
                          equals straight M to the power of straight a plus straight b end exponent straight L to the power of negative straight a plus straight b end exponent straight T to the power of negative 2 straight b end exponent
Comparing the dimensions of M,L and T on both sides, we get
                         space space straight a plus straight b equals 0 comma space

minus straight a plus straight b equals 1
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On solving we get, 
             straight a equals negative 1 half space space and space space straight b space equals space 1 half 
Thus,   space space space space straight v equals KT to the power of 1 divided by 2 end exponent straight m to the power of negative 1 divided by 2 end exponent 
rightwards double arrow             straight v equals square root of straight T over straight m end root