First, I want to announce the Repurpose Contest page is up. This includes pictures of the items for the April 2012 contest.

This episode is the next step in complexity from Episode 25. The problem is very similar to the last one except the force and the rope are connected at different points.

it is impossible at this point to determine the vertical forces because two of them are unknown.

Again this has two unknown forces. All we are able to determine is that they are equal but opposite. Please note these forces are drawn above the beam for clarity, but the forces act on the center of the beam.

This 3rd diagram gives us only one unknown.

500 – (10*Rv) = 0 –> Rv = 500/10 = 50.

The rope must pull up with 50 Lbs.

Going back to the Vertical force diagram:

Rope Vertical + Post Vertical – 100 = 0

Post Vertical = 100 – 50 = 50 Lbs.

To calculate the Horizontal forces we must create similar right triangles the physical drawing, only this one will be scaled in forces. The side opposite the 30 deg angle will be sized for 50 Lbs. After it is all drawn out, the answer will be the Rope Horizontal force will be 86.6 lbs.

Finally from the Horizontal force diagram we are able to calculate the Post Horizontal force which will also be 86.6 lbs.

This is probably the last example of statics we will go through for awhile. I hope to point you toward a good book on the subject if you want to continue on with this. (As soon as I find a good current one – mine is out of date.) .

Gary

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