Phy about force

I guess you are asking for the tension in a string when it is stretched.

Assume the two strings (one long and one short) are of the same material and of the same cross-section area, the long string will have lower tension than the short one when both are stretched with the same extension.

Since by Hooke's Law,
F = k.x
where F is the force on the string
x is the extension of the string
k is the force constant

But k = E.A/L
where E is the Young's modulus of the material that made by the string
A is the cross-sectional area
L is the (natural) length of the string

Hence, we have F = [E.A/L].x
When all quantitieis are the same, longer L gives a smaller force (tension) F

long string or short string is not related to their tension.
A strong tension or weak tension is about the angle between horizontal and the string.
If the angle is small ,then the tension is big (because Tension = weight / sin x)

2007-03-31 13:59:41 補充：
I am talking about the string which can't be stretched.