Forces can be applied to solids. For rigid solids, forces can be applied in the form of compression or tension forces. Compression forces act to decrease the length of a solid, whereas tension forces act to increase the length. Tension forces, but not compression forces, can also be applied to nonrigid solids, such as a piece of elastic.

Tension is defined as a kind of force which is responsible for the stretching of a material. Let us see some example of tension which are common in our day to day life.
 Cable used in a crane
 Stretched rubber band
 A bolt, when the nut is tightened
Tension can be represented by T, the formula for calculating the tension force is given as,
T = mg + ma
m is the mass
a is the acceleration
T = W + ma
orT = mg + ma
T = m (g + a)
Where W = weight of a materialm is the mass
a is the acceleration
Surface tension is a characteristic property of a liquid. In this property, all liquids have a tendency to contract its surface in order to acquire minimum surface area. So this surface appears like a stretched membrane. Quantitatively surface tension is,
Where F is the force acting on an imaginary line of length l, drawn tangentially to the liquid surface at rest.
Surface tension is also defined as the work done per unit area in increasing the area of the liquid film at constant temperature.
Some solved problems of tension are given below: T = $\frac{F}{l}$
Where F is the force acting on an imaginary line of length l, drawn tangentially to the liquid surface at rest.
Surface tension is also defined as the work done per unit area in increasing the area of the liquid film at constant temperature.
T = $\frac{Work\ done}{Expansion\ in\ area}$
Solved Examples
Question 1: An elevator of mass 500kg is hanging in a cable. Calculate the tension in the cable if the elevator is moving with an upward acceleration of 2m/s^{2}?
Solution:
Given parameters are,
m = 500kg, a = 2m/s^{2}, g = 9.8m/s^{2}
T = m (g + a)
T = 500 (9.8 + 2) = 5900N
Solution:
Given parameters are,
m = 500kg, a = 2m/s^{2}, g = 9.8m/s^{2}
T = m (g + a)
T = 500 (9.8 + 2) = 5900N
Question 2: An object of mass 150kg is suspended in a rope, if that object is moving with a downward acceleration of 1.5m/s^{2}, calculate its tension?
Solution:
Given that,
m = 150kg, a = 1.5m/s^{2}, g = 9.8m/s^{2}
T = m (g + a)
T = 150 (9.8  1.5) = 1245N
Solution:
Given that,
m = 150kg, a = 1.5m/s^{2}, g = 9.8m/s^{2}
T = m (g + a)
T = 150 (9.8  1.5) = 1245N