# Help with Strength of Materials question

1. Feb 11, 2007

### 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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2. Feb 11, 2007

### Staff: Mentor

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 text book?

3. Feb 11, 2007

### Pyrrhus

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

4. Feb 11, 2007

### kamikazi929

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

5. Feb 11, 2007

### Pyrrhus

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.

6. Feb 11, 2007

### kamikazi929

Moment-Area and Double Integration sounds familiar

7. Feb 11, 2007

### Pyrrhus

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?

8. Feb 11, 2007

### kamikazi929

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

9. Feb 12, 2007

### kamikazi929

totally hit a brick wall with this one :(

10. Feb 12, 2007

### Pyrrhus

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