Calculating Net Force: Lever with Two Fulcrums & Beam Hit at 7 Feet

[jackrabbit]

I am trying to figure out the net force of around a fulcrum (actually two fulcrums). For ease, assume the following hypothetical and ignore the weight of the beam itself in the calculations:

There is a beam that is 21 feet long that is being lifted by a crane. The left end is at "0 feet" and the right end is at "21 feet."

There are three points along the beam.

Point A: Located at 0 feet, with a downward force of 3 pounds.

Point B: Located at 14 feet. This is where the cable from the crane is attached to the beam. The cable is lifting with a force of 12 pounds.

Point C: Located at 21 feet, has a downward force of 8 pounds.

When the crane lifts the beam, the beam will rotate around Point B (meaning that Point C will not tilt toward the ground).

Now assume that, as the crane lifts the beam, the beam hits a branch at Point D, located at 7 feet. How do I determine which way (or whether) the beam will rotate around Point D?

 

[LightHero]

To determine which way the beam will rotate around Point D, you need to calculate the net force acting on the beam. The net force is the sum of all the forces acting on the beam (in this case, the downward force at Point A, the upward force at Point B, and the downward force at Point C). The net force acting on the beam can be calculated as follows: Net Force = (3 lbs) + (12 lbs) - (8 lbs) = 7 lbsSince the net force is positive, the beam will rotate clockwise around Point D.