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BananaJelly
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This is a problem from Michael Lindeburg's FE Review Manual. It is in Chapter 20, Number 11 if you have the book.
PROBLEM:
There is a picture of a cantilever 2 m in length attached to a wall. There is a force applied at a 30 degree angle from the horizontal at the free end of the beam.
"The beam is manufactured from steel with a modulus of elasticity of 210 GPa. The beam's cross-sectional area is 37.9 cm^2; its moment of inertia is 2880 cm^4. The beam has a mass of 45.9 kg/m. A 6000 N force is applied at the top of the beam, at an angle of 30 degrees from the horizontal. Neglect buckling.
What is the approximate maximum bending moment in the beam?"
SOLUTION:
I have the solutions, but I cannot understand the first part of it:
The moment due to the beam's own mass is
M1 = (0.5)wL^2 = (0.5)(45.9 kg/m)(9.81 m/s^2)(2 m)^2
I do not understand where they got the "(0.5)" from. If it is moment, shouldn't the equation just be M = F L = mgL = (wL)(g)(L) = wgL^2 without the 0.5 in front?
There's more to the solution, but I am stuck at this one part regarding the moment due to the beam's mass.
PROBLEM:
There is a picture of a cantilever 2 m in length attached to a wall. There is a force applied at a 30 degree angle from the horizontal at the free end of the beam.
"The beam is manufactured from steel with a modulus of elasticity of 210 GPa. The beam's cross-sectional area is 37.9 cm^2; its moment of inertia is 2880 cm^4. The beam has a mass of 45.9 kg/m. A 6000 N force is applied at the top of the beam, at an angle of 30 degrees from the horizontal. Neglect buckling.
What is the approximate maximum bending moment in the beam?"
SOLUTION:
I have the solutions, but I cannot understand the first part of it:
The moment due to the beam's own mass is
M1 = (0.5)wL^2 = (0.5)(45.9 kg/m)(9.81 m/s^2)(2 m)^2
I do not understand where they got the "(0.5)" from. If it is moment, shouldn't the equation just be M = F L = mgL = (wL)(g)(L) = wgL^2 without the 0.5 in front?
There's more to the solution, but I am stuck at this one part regarding the moment due to the beam's mass.