Engineering Statics

A-4


A communications cable is attached at point C to the pole. Knowing that the tension in the cable, T1, is 800 1b., determine the tension in the cable on the right side, T2, required if the resultant, R, is to be vertical. Determine the magnitude of the resultant, R.

The first thing we do is identify the x and y axes, 
creating a diagram of the forces with a frame of reference.
The resultant of the two forces can be divided into components in the i and j directions.
The x components are added together to get the resultant's x component in the i direction.
Similarly, the y components are added together to get the resultant's y component in the j direction.
But remember that the resultant is vertical, so the sum of the x forces is zero.
Summing the forces in the x-direction, and knowing that they are equal to zero, we can solve for tension T2.
We solve for tension in T2.
We then reduce the resultant vector, R.
The magnitude of the resultant can be determined using the Pythagorean Theorem.