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Thread: speed of stationary wave in a string

  1. #1 speed of stationary wave in a string 
    Junior Member
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    Dear all,

    In my text book it is written that when a string clamped at both ends oscillates in it's fundamental mode then the frequency of the stationary wave set up in the string is given by f=v/2l .where 'f' means frequency,'v' means speed of wave and 'l' is the length of string.following are my doubts
    1.since wave is stationary not travelling so its speed should be zero always?if it is not then what is the meaning of speed in a stationary wave and what is its formula?
    2.they used the formula v=square root of T/m.where 'T' is the tension in string and 'm' is the mass per unit length of the string.but as far as i know this formula is derived for a travelling wave not for stationary wave then why did they use it.please explain

    Thanks
    Arvind
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  2. #2  
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    Quote Originally Posted by arvindsharma View Post
    Dear all,

    In my text book it is written that when a string clamped at both ends oscillates in it's fundamental mode then the frequency of the stationary wave set up in the string is given by f=v/2l .where 'f' means frequency,'v' means speed of wave and 'l' is the length of string.following are my doubts
    1.since wave is stationary not travelling so its speed should be zero always?if it is not then what is the meaning of speed in a stationary wave and what is its formula?
    2.they used the formula v=square root of T/m.where 'T' is the tension in string and 'm' is the mass per unit length of the string.but as far as i know this formula is derived for a travelling wave not for stationary wave then why did they use it.please explain

    Thanks
    Arvind
    A stationary or standing wave is set up by two waves travelling in opposite directions and adding together. These are what have the speed.
    Standing wave - Wikipedia, the free encyclopedia
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  3. #3  
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    As per Jilan individual waves have speed and i also agree with this but stationary wave should have zero speed because velocity of both the waves is in opposite direction so it must cancel each other.please clear this doubt.
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  4. #4  
    Senior Member Strange's Avatar
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    The speed is the speed a wave would travel along the string. You can think of the standing wave as bouncing backwards and forwards at that speed and appearing to stand still because the wavelength matches the length of the string.
    arvindsharma likes this.
    You can do everything right, strictly according to procedure, on the ocean and it'll still kill you, but if you're a good navigator at least you'll know where you were when you died.
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