Physics Help Forum How far will the middle point of the beam sag under load?

 Equilibrium and Elasticity Equilibrium and Elasticity Physics Help Forum

 Apr 22nd 2019, 03:09 PM #1 Junior Member   Join Date: Apr 2019 Posts: 1 How far will the middle point of the beam sag under load? There is a wooden beam with given size. We put 1kg in the middle point of beam. Question is how much will the middle point lower itself? Young modulus is 1,18x10^10 Pa Size of beam: length 1 meter , other two dimensions are 5cm and 0,5cm The beam is supported on the ends of it. We haven't learnt about this topic yet but I would like to have the answer. Is here anybody who would solve it for me please?
 Apr 24th 2019, 04:43 AM #2 Senior Member     Join Date: Jun 2016 Location: England Posts: 1,000 Not Ignoring You Hi, I think you will find this is one of those "easy when you know how" problems. However, unless you are actually working in a field that requires you regularly exercise this knowledge, you are unlikely to know it "off the top of your head". I had a quick poke around on the internet to see if I could find enough pointers to work out how to do it, but then thought #insert expletive to taste# it, you yourself say that you are expecting this to come up soon in your tuition. Perhaps you can come back when your tutor has explained it to you, and explain it to us... __________________ ~\o/~ Last edited by Woody; Apr 24th 2019 at 04:47 AM.
 Apr 24th 2019, 07:28 AM #3 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,352 You can find formulas on line for beam equations, and a little searching would lead you to the formula for max deflection of a simply-supported beam with point load at the center: $\delta = \frac {FL^3}{48 EI}$ You can determine the beam's moment of inertia, I, from the cross-section dimensions you provided. You will have to look up the value of Young's modulus, E, for the material the beam is made of. Woody likes this.

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