Maximum beam deflection...please help!

[roxstar1]

The deflection, D of a particular length, L is

D = 2(x^4)-5L(x^3)+3(L^2)(x^2)

where x is the distance from one end of the beam. Find the value of x that yeilds the maximum deflection. :evil:

 

[Guest]

In this problem you have 2 variables and 1 fixed value -- the variables are D and x , note the L is a fixed value.

dD/dx = 8x^3 - 15Lx^2 + 6(L^2)x

this is a quadratic form if you take the common factor of x out of it, the max or min occurs when dD/dx =0

then do the second derivative to confirm the max or min....

hope this helps.

 

[roxstar1]

Thanks so much for the advice! I finally got the right answer