A uniform steel girder of weight 22kN and length 14m is lifted off the ground at one end by a crane. When the raised end is 2m above the ground, the cable is vertical.

Calculate 1) the tension in the cable at this position and 2) the force of the girder on the ground.


Any help would be greatly appreciated.

First consider the moments taken about the point where the girder touches the ground: you have the weight of a 22 kN mass pushing down, and if you assume the girder is uniformly constructed the location of that weight can be assumed to be at the mid-point of the girder's length. And you have the tension in the rope at the far end of the girder pulling up. The sum of these two moment is zero - so now you can calculate the tension in the rope to make that so. Then determine the force against the ground by considering that the sum of all three forces acting on the girder - the tension in the rope plus the force of the ground minus the weigth of the girder - must sum to zero.

Thank you sooo much - I finally got the answers thanks to your help. My physics teacher has been ill and won't return before the exams in May - so you were truly a great help. Again many thanks.

You are welcome!