A cord of mass 0.65 kg is stretched between two supports 8.0 m apart. If the tension in the cord is 120 N, how long will it take a pulse to travel from one support to the other?
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This is Giancoli Answers with Mr. Dychko. The speed of a wave on a cord is going to be square root of the tension in the cord divided by its mass per unit length. And so μ can be replaced with m divided by l. And FT divided by m over l is the same as FT times l over m because we can multiply top and bottom by l and these l's cancel here, we're left with an l multiplied by the thing on top. So, speed is square root tension times length divided by mass of the cord. The time it takes to go from one end of the cord to the other is going to be that distance which is l divided by the speed. And instead of dividing by this we're going to multiply by its reciprocal. So, it's going to be l multiplied by square root of m over FT l. And this, you know, this works out to l over square root l times square root m over FT, you can think of it that way. And this is square root l. And I put that underneath the square root sign. So, we have time as square root m l over tension force. So, that's 0.65 times 8 meters divided by 120 newtons which is 0.21 seconds.
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