I don't exactly know what your teacher wants you to talk about in your paper, but here's what I would write about.
- Newton's first law: equilibrium. This beam is going to have two opposite and equal forces: the Load of w/e weight, and the base of this beam is going to produce a normal force so that your beam actually stands (otherwise it'll crumble).
- Torque. I'm assuming that one side of your beam is going to be fixed to a rigid end and that the other side is free and that the load would be attached there. You also have to figure out the internal moment around the fixed end of the beam so that the summation of the moment about your whole beam is in equilibrium (otherwise your mean is going to succumb and collapse)
- Know the difference between compression and tension. These are both forces, but remember beams are two-force members, meaning their internal forces are axial and 1 dimensional. So Statically, their internal forces will either be pointing towards each other or away from each other (being tension and compression respectively). When making any beam, it is crucial to know which of these two forces are greater and to know whether the material used is capable of withstanding greater compression or torque
- Stress and strain. Stress is equal to the internal force of the beam over its cross sectional area (i.e. if your beam is a long circular tube, then the cross sectional area is pi*radius^2.) Not that you have to actually calculate the maximum stress newspaper can withstand, but when it comes to making any beam, understanding of the ultimate stress of any material is crucial in determining how safe your beam is going to be. Strain is the elongation per unit length. So it equals delta/original length. And to calculate delta, you have to know the internal force of the beam (and to calculate this, you have to figure it out through free body diagrams) and you have to know the modulus of elasticity of the material.
- Deflection, this is where when a beam is laterally loaded, the whole beam will be bent concave downwards (assuming that the load is vertically downwards). Again you have to know the modulus of elasticity of the material as well as its Inertia
- Trusses and joints. If the whole structure is going to use more than one beam, then there are going to be multiple trusses and joints. In order to calculate the internal forces of each beam, you have to a free body diagram around each joint and use newton's first law to calculate the forces of each beam. One must note the difference between x directional and y directional forces.
- Torsion is important. Torsion is the twisting force about a beam. Torque = Shear stress/radius of cross section of beam *polar moment of inertia. If the beam is circular, then the moment of inertia = PI*diameter^4/32. If the beam is hollow, then it's simply PI(D_outer^4-D_inner^4)/32. If the beam is a rectangle, then the moment of inertia is = bh^3/12. One must note whether this is the x or y directional moment of inertia. Also one must know about the righthand rule. When a torque is applied clockwise about a point, it points up, and vice versa. Like with forces, Torques must also be in equilibrium
- Since this class is physical science afterall, I would primarily talk about the properties of the materials that would be used. Like whether they are inelastic or w/e.
Post has been edited 1 time(s), last time on Mar 4 2008, 6:25 am by MillenniumArmy.
None.