What is the equation for tension in a string?

[The Sword 88]

My physics book sucks and I can't find the equation for tension in a string, can some one tell me the equation?

 

[dextercioby]

My physics book sucks and I can't find the equation for tension in a string, can some one tell me the equation?

What kind of string??Is it one which oscillates,in which mechanical waves propagate??If so,then it should be
$$T=m\frac{\partial^{2}u(x,t)}{\partial t^{2}}$$
,where "u" is the amplitude of the wave which propagates along the "x" axis,or it is the coordinate "y" of a point on the string at point "x" at the moment "t".

Daniel.

 

[HallsofIvy]

Or, if the string is massless, hanging from a support and supporting a weight W, then the tension at every point in the string is W. (Your text may have thought you didn't need a formula for that!)

If the string has weight density μ and is supporting weight W, the the tension at a point a distance x above the weight is μx+ W, the total weight below the point.