Not sure if I'm applying the formula correctly. I'm trying to find the deflection in a cantilever beam that is loaded by a uniformly-distributed load. The formula is:

$$v=- \frac{wx^2}{24EI}(x^2+6L^2-4Lx) $$


$$v = \text{Deflection} \\ x= \text{Distance from wall} \\ w=3\ \text{kN/m} \\ E=200\ \text{GPa} \\ I=986e6\ \text{mm}^4\\ L=10.5\ \text{m}$$

So for $x=10.5\ \text{m}$ I'm getting: $$v=- \frac{3000(10.5)^2}{24*200e9*986e6}(10.5^2+6*10.5^2-4*10.5*10.5) \\ v=-2.31e-14$$


1 Answer 1


You've converted w into N/m, E into N/m2, but you've left I in mm4.

So, dividing I by 1e12, your answer multiplies by 1e12, giving v = 0.0231m, or 23.1mm. Which sounds like a sensible answer.


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