Suppose that a string is pulled tight and held under some tension T. If we strike one end of the string with a hammer, it will cause a disturbance -- a travelling wave -- to move along the string. The speed of that wave depends on the tension and on the nature of the string; specifically, its linear mass density μ.
If you know the tension and the linear mass density, then it's easy to compute the speed of the wave:
Don't forget that we have already learned some other relationships between the speed of a wave and other quantities ....
