Today in class we named the forces we already know: tension, gravity, the normal force, friction, and drag, which is the force from a fluid.
If a 5 kg string is hanging on a string connected to a ceiling, what is the tension in the string?
We drew a force diagram with the down arrow representing the Force of gravity from earth on the weight and the upward arrow of equal magnitude representing the Force of tension from the ceiling on the weight. The weight of the weight equals 50 N because the gravitational field strength equals 10 N/kg. Therefore, for every 1 kg of increase, there's an increase of 10 N. Since the earth is pulling down on the weight with a force of 50N, the tension in the string equals 50 N. Tension is the same everywhere in the string.
Strong Man problems:
If one horse weighs 800 N, the tension on the rope between the man and the horse equals 800N. The tension in the other rope the man is holding, whether another horse or a tree is attached to the other end, equals 800N. The tension of the rope between the man and two horses, weighing 800 N each, is 1600 N, and the tension of the rope between the man and the tree is 1600 N. If the 800 N horse is attached to the tree with a rope, the tension in the rope is still 800N.
Vectors in force diagrams:
You can make triangles out of a force diagram by using vector addition or vector components. Vector addition involves lining up the individual vectors tip to tail. This method is commutative, meaning that you can add the vectors in any order. To use vector components, draw dashed lines on the force diagram to make a right triangle using one vector and to represent the other vectors.
Just because a force diagram has three lines doesn't mean they can form a right triangle.
Look at the Forces and Force Diagrams handout for a better definition of component vectors.
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