Calculating Force of Beam on Support at A

In summary, the man builds a UDL platform with a mass of 100 kg and a length of 7 meters. The beam is supported by two sawhorses and the man stands over the support at point B. The force exerted by the beam on the support at A is the same as the force of A on the beam.
  • #1
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A man of mass mm = 95 kg decides to paint his house. To do this, he builds a platform using a uniform beam with a mass of mb = 100 kg and a length of L = 7 meters. The beam is supported by two sawhorses, as shown in the diagram above.

If the man stands over the support at point B, calculate the force exerted by the beam on the support at A.

--at first, i misread the question and thought it's asking for the force exerted by A on the beam.
and I did the following:

F(A) + F(B) - F(b) - F(m) = 0

and have B as the pivot,

thus with the torque of A = -3 F(A)
and torque of beam (b) = .5 F(b)

, but now it's asking of the F exerted by beam on support at A? I'm confused here...its one whole beam, I'm assuming the force excerted by the beam will occur at the center of mass...help
 

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  • #2
The force of the beam on A is the same as the force of A on the beam. (For every action there is an equal and opposite reaction)
 
  • #3
yea, i initially thought it's asking for F(A), and i tried solving for it, didnt work out, unless i did something wrong in my original calculations...
 
  • #4
I can't understand why you've been asked the same question twice, but disregrding that, there's a mistake in caculating the torque of the beam.
The beam is a UDL, not a point load acting at its mid-point.
You have to consider the torque from the beam as being up of two parts. one to the left of point B and one to the right.
 
  • #5
There are two forces of the beam. Since the beam is uniform we can say that one meter has a mass of 100/7 kg. Since two meters are located on the other side of B from the other 5 meters of the beam, you must take that into account as well.

We'll designate the 5 meters to the left of B as b1. The two meters to the right of B shall be called b2.

The problem can be set up as total torque being zero (since it isn't moving). There for the expression for the torque caused by each point is: t(b1)-(t(A)+t(b2))=0. Remember that the torque resulting from the weight of a section of beam essentially acts midway between the end of the beam and the pivot point.
 

What is the formula for calculating the force of a beam on support at point A?

The formula for calculating the force of a beam on support at point A is F = (W x L) / 2, where F is the force, W is the weight of the beam, and L is the length of the beam.

What units should be used when calculating the force of a beam on support at point A?

The units used for calculating the force of a beam on support at point A should be consistent. Common units for force include Newtons (N) and pounds (lb).

How do I determine the weight of the beam when calculating the force on support at point A?

The weight of the beam can be determined by multiplying the density of the material by the volume of the beam. The density can be found in a materials table or measured directly. The volume can be calculated by multiplying the length, width, and height of the beam.

What other factors should be taken into account when calculating the force of a beam on support at point A?

In addition to the weight of the beam, other factors that should be considered when calculating the force on support at point A include the load on the beam, the distribution of the load, and any external forces acting on the beam.

Can I use the same formula for calculating the force of a beam on support at different points along the beam?

Yes, the same formula can be used to calculate the force of a beam on support at different points along the beam. However, the weight and load of the beam may vary at different points, so these factors should be adjusted accordingly.

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