SIMPLIFIED: "4.6: Common Forces - Tension"

Link to article: https://phys.libretexts.org/Courses/Georgia_State_University/GSU-TM-Physics_I_(2211)/04%3A_Forces/4.06%3A_Common_Forces_-_Tension 

Note: The image above was taken from the original article.

The article linked above is all about tension force. Tension force is a bit hard to describe, but it is basically a force through a rope, string, or cable. Essentially, if you tie a rope to a box and you are pulling on the rope, then there would be a tension force. As an important note, you cannot push something with a rope, so tension forces will always be a pull with one of the things I just mentioned (like rope, string, etc.). 

There is no exact formula to calculate tension force. You calculate it as you set up your net force equations when you are solving physics problems. For example, let’s say that there is a box hanging from the ceiling through a string. In this case, because the box is hanging and motionless, the tension force and the force of gravity are equal in magnitude (if gravity was greater than the tension force in this scenario, then the box would come accelerating downwards). Therefore, the force of tension (which is just denoted with T of F_T) is equal to the force of gravity, which is calculated through the formula: mass * acceleration due to gravity (g). 

Let’s do a quick example problem. If an object that is 10 kilograms is hanging from the ceiling due to a string, what is the tension force? Well, the tension force is equal to the force of gravity. The force of gravity is calculated through m * g. Therefore, since the mass is 10 kg, and g is 9.8, 10 * 9.8 is 98 newtons. Thus, the force of tension in this scenario is 98 newtons.

Things are not this easy when the box is hanging straight downwards. In some problems, the object tied to a rope or string will be at an angle, and this will complicate the problem a bit.