# Help with Strength of Materials question

• kamikazi929
In summary, The conversation discusses finding the deflection at a specific point on a beam and the methods that can be used to solve it. The beam has a downward point load and a moment at specific distances from the left end. The two main approaches to solving this problem are the geometric and energetic methods, which include double integration, superposition, moment-area, conjugate beam, virtual work, and Castigliano's Theorem. It is suggested that the student pick one method and start working on it.

#### kamikazi929

if anyone could provide any insight as to how i go about completing this question i would be grateful, i was off the week this was taught to the group and have no idea whatsoever

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Well one is to find the deflection at 3m from the left end of a 6 m beam, which is therefore the midpoint.

There is a downward point load of 85 kN at 2 m from the left end and moment of 100 kN-m at 4 from the left end.

Do you know the convention on moment? The 100 kN-m moment will raise the portion of the beam on the left side, will lowering the portion of the beam on the right side, of the moment.

Do you have examples from your textbook?

What methods do you know? Geometric and/or energetic?

thats the thing, i had a berievement in the family and I was off college for a good time, just managing to catch up but this is in my way. missed the whole section on deflections

I'll name a few:

Geometric Approach:

Double Integration
Superposition
Moment-Area
Conjugate Beam

Energetic:

Virtual Work
Castigliano's Theorem

any of them is in your course syllabus?

Usually a regular Mechanics of Material course will cover the three first geometric methods. An advanced course may include also Castigliano's Theorem.

Moment-Area and Double Integration sounds familiar

If its Double Integration, you will simply need to work with the differential equation:

$$\frac{d^{2} \nu}{dx^{2}} = \frac{M}{EI}$$

Moment-Area has two theorems, you'll need to work out.

why don't you pick one and start?

ill give it a bash now see what i come up with

totally hit a brick wall with this one :(

kamikazi929 said:
totally hit a brick wall with this one :(

Why don't you show us what you did, so we can actually help?