Asked by Katie
on 20 Mar 2013

The equations governing the forces on the beam shown below are as follows:

F_ax=0

P=F_ay+F_by

P=(5.*F_by)./10

We want to determine the maximum load, P, which will result in a load at the roller, F_by, which does not exceed 500 lb.

Write a Matlab program which uses the above system of equations to determine the maximum force P which results in vertical force on the roller, F_by of between 499 lb and 500 lb. Your approach should repetitively solve the above system of equations until the desired result is obtained.

This is the code I have, but I don't know where to go next:

F_ax=0

F_by<=500 %lbs F_by>=499 %lbs

P=F_ay+F_by

P=(5.*F_by)./10

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Answer by bym
on 21 Mar 2013

So, when I see a problem statement that says "solve the above system of equations" I think of formulating the equations in matrix form. The coefficient matrix for the equations involving P is

c =

1.0000 1.0000 0 0.5000

when I see a problem statement that says "... until the desired result is obtained", I think of a loop structure

doc while

when the problem statement says "[repetitively] solve..." The repetition is taken care of in the loop, but solving usually involves finding the unknowns. this often involves mldivide

doc mldivide

As you can see, I haven't given you the direct answer, but areas to explore in solving your homework problem

bym
on 22 Mar 2013

doc command is just a way of getting to the help documentation from the command line. As far a getting the coefficient matrix, it is a matter of writing out the equations and putting the coefficients into a matrix, e.g.

`1*F_ay+1*F_by = P`

`0*F_ay+.5*F_by = P`

equals

`[1,1;0,.5]*[F_ay;F_by] = [P;P]`

Opportunities for recent engineering grads.

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