# Search results

1. ### Was bored today and searched for a puzzle. Came across this one....

https://www.mensa.org.uk/puzzles/brainteasers?page=470
2. ### Was bored today and searched for a puzzle. Came across this one....

Hmmm...appears to have turned out that the question actually wasn't trivial at over 40 replies later. This is because of the question's poor wording. It is a trivial question if it is worded correctly. Thanks for the solution that was posted which cleared up the confusion for me. And no it...

4. ### Was bored today and searched for a puzzle. Came across this one....

So I am missing something in this one. The answr is 8. Can someone explain? In a department store, with only one girl working on the gift-wrapping service, four gifts per hour were wrapped in the first 15 hours. With help from a colleague for the next 45 hours, the amount of gifts wrapped...
5. ### Statics problem

I went ahead and solved it. There is actually one other step I used prior to summing moments about point C. You still have to isolate part of the structure as noted above which is the most important idea for this problem. I also found your vertical reaction at D looks like it is going in the...
6. ### Statics problem

the reactions at the supports look correct. you need to isolate the top portion of the structure (sum moments about C) to start getting answers.
7. ### Statically indeterminant problem

I summed moments about A and the resultant of the components shown doesn't go through point A so you can get V2 and therefore V1. I just solved the rest of it with what he gave assuming a RIGID BODY, using superposition and the geometry given. The additional equation is that H1=H2 for each...
8. ### Statically indeterminant problem

This probably should be placed in the homework help section. Your original resultant force appears to go through point A (ie. try summing moments about point A to start finding reactions).
9. ### Need help determining force behind certain vectors

Make a FBD of the weight with the 2 cables cut. Sum forces in the horiz and vert directions to get the force in each cable.
10. ### Static tests of timbers in structural sizes (ASTM D198-84)

I know wood grows on trees, and I never said you shouldn't estimate it for general purposes from the NDS handbook. Anyone (you?) that has done experimental work would know that you also want to verify the properties EXPERIMENTALLY for the specimen you are working with for your data and not just...
11. ### Static tests of timbers in structural sizes (ASTM D198-84)

I still say that you want to measure the modulus of elasticity for the actual piece of wood that you have, and not pull the modulus from NDS tables. This is because you are under experimental circumstances and not design. Alephzero is likely correct about bearing failure at the supports, but...
12. ### Trying to make a cantilever with the highest efficiency

A triangle shaped truss should give the least material for a required strength. But I normally can't use these in practice because of the depth required for them. The most common case you will find is floor beams that are cantilevered out to create a balcony, or roof beams that are...
13. ### Static tests of timbers in structural sizes (ASTM D198-84)

I have not done this test but I have done the same bending test setup on concrete beams. I would say when rupture of the bottom wood fibers occur visually, and this should correspond to a maximum on the loading data recorder. You should see from the recorded loading data a maximum load point...
14. ### Finding the reaction of a beam

Go through the statics tutorials. http://web.umr.edu/~bestmech/ [Broken]

Use virtual work. Set the deflections equal for each case and solve for P. I would guess this is how your instructor wants it to be solved and not just by manipulating existing tables.
16. ### Civil Engineering - Structures

It pisses me off as much as you, trust me. So how do we fix it? Well that will be the choice of the state. I agree. But most engineers are stupid in terms of business so I doubt there will be an agreement reached. If you want a real discussion on this, join and post to the SEAINT...
17. ### Civil Engineering - Structures

I agree with everything that Structural Guy said except about the Master's degree. More companies are looking for structural engineers with Masters degrees, and ASCE is even trying to make it where you can't get a PE license without one (even though I doubt it will be accepted). You will have...
18. ### Civil Engineering - Structures

You have to start somewhere. All you need is a BS degree to get a PE license. Depending on the company and the part of civil you go in, a Master's may be required (several structural engineering companies I have looked at lately require an MS degree). I don't think I have ever seen it required...
19. ### PE license for Civil and mechanical engineers

I work at a multi-discipline company (electrical, mechanical, civil, structural, arch.) and it is every engineer's goal there that I know to get licensed. There is an increase in salary after you get it and it increases the company's credentials when bidding on projects to have 'X' number of...
20. ### Wanted: Stress and Strain Tutorial

Beginning basics http://web.umr.edu/~mecmovie/index.html [Broken]
21. ### Is Structural Integrity related in any way to Static Friction? Or vice versa?

Friction is usually taken into account in structural design for cases like sliding of retaining wall footings on soil. Friction is of course part of the reality that makes a structure work as well as lots of other things (if there were no friction, "slip critical bolts" would not work). But...
22. ### Method Of Joints

Method of joints refers to balancing forces at the internal joints of trusses in order to find all the internal member forces. If you have a statics book there should be examples to follow, it is pretty easy.
23. ### Calculating forces vectors etc?

Does that mean only one of the guy wires will actually be attached or both of them?
24. ### Equilibrium of Coplanar Force Systems HW Problem

It is just making a free body diagram with the cable detached from the support. That is how I found the force in the cable. There are 3 steps; sum moments about A with the cable cut to get the cable force (note the cable is conveniently perpendicular to the platform), then sum vertical forces...
25. ### Equilibrium of Coplanar Force Systems HW Problem

I got it now, I had left out a cosine. Make a cut through the cable up at where it attaches to the top support. Then sum moments about point A using the vertical weights given in order to find the tension in the cable.
26. ### Equilibrium of Coplanar Force Systems HW Problem

Are the answers 143.6 and 445 and 71.8?
27. ### Isoceles triangle in absolute geometry

I see where the lengths would be equal for a sphere but not this case for the circle.
28. ### Corrosion of STEEL

I believe the layer of corrosion protects it. Corrosion rates are higher in moving water because the corrosion covering is always being washed away.
29. ### Statics physics question

The question wants you to minimize the force in the cable "F". So in order to do that, you would want to find the angle and magnitude of the resultant of forces given already (like it says to do) then make "F" parallel with this force (at the same angle). So first break apart the given forces...
30. ### Load under sand pile.

Along the top surface, I would look at the force at any location as equal to the vertical weight of the soil directly above. So at the middle of the top surface, force=density*(h-d). And it is a linear decrease down to force=density*h2 at the left and right side of the top. It is basically just...
31. ### Pressure drop

http://www.lmnoeng.com/HazenWilliamsDesign.htm
32. ### Load under sand pile.

Is this similar to what you are describing? http://www.angelfire.com/linux/haynewp/
33. ### Some Tough Problems (for me at least)

You could even reduce the last problem down to a single step, your final equation F3=2.4m(170kg)(9.8)/0.8m can be gotten directly by summing moments about the top left corner of picture, where F1 and F2 intersect.
34. ### Some Tough Problems (for me at least)

OK, I take the "contact forces" to mean you have a single horizontal reaction at the ridge and a single vertical reaction at the connection to the wall. I would not think any joints to be moment resisting in this problem. The snow should be modeled as a single concentrated load at the...
35. ### Engineering Forums?

I have hung around eng-tips.com mostly also, but I agree their software is the worst. I like physicsforums because there is a wide variety of knowledge and the software is great. Here is one where the environment is much improved, but it just starting so there are very few members and posts...
36. ### Basic Air Conditioner Question

I see now, I was thinking of it as adding energy to the fluid as a result of the work done during the compression process.
37. ### Basic Air Conditioner Question

I have been trying to learn how home air conditioners work since I had some problems yesterday with my split system. I was reading here: http://www.energyquest.ca.gov/how_it_works/air_conditioner.html This is a stupid question and basic mechanical engineering, but there is something about...
38. ### Forces in trusses

The first part is right about AE but you can't assume EF=Ex because there is also member BE framing into the joint you have to analyze.

It sounds like you can approximate it as a uniform weight suspended cable problem. http://tinyurl.com/rmv6w
40. ### Simple statics

You're doing too much work. You can solve for CD by just balancing the free body of member ABC now that you have the reactions at A. CD is a 2 force force member so it only has axial force (in its X direction), but you still have to apply the 10,000lb load to joint C in the Y direction when...
41. ### Lawn Mower Problems

I am too cheap to buy a new one without someone else looking at it first. But I certainly was thinking about it today as I was cranking my ass off in the sun.
42. ### Lawn Mower Problems

I cleaned off the plug and it is still doing the same thing and I have sprayed a half a bottle of cleaner in the carb. I want to try new gas but I have of course got to find a place to get rid of the old gas first. The mower is practically brand new and the gas doesn't look irregular. The gas...
43. ### Lawn Mower Problems

I have a lawn mower that has not been run in over a year. I bought it new and I haven't run it but 3 or 4 times back over a year ago. Now it won't start. Well, it will start when I spray carb cleaner into the carb and it will stay running as long as I keep spraying the cleaner into the carb...

I would expect the same out of ordinary building inspectors in my area. They will note any obvious deficiencies but don't run loads and check member requirements. Try one of these guys. If they are "P.E." they should be able to run loads and check member sizes and connections after they conduct...

46. ### Under too much stress I just zone out

That is very different than the way I handle too much stress. Maybe set a time schedule for yourself on when you are going to spend time on the software class. What happens to me when I am overstressed is my performance goes down and I try to overcompensate.
47. ### Mechanics Question III

You basically have it. Your equation 1500*5-W(4-x)=0 is right and the other is just 1000*5-W*x=0 (if x is measured to the right of C) Now you need to solve the 2 equations and 2 unknowns.
48. ### Levers and UTS

It is a cantilever beam, cantilevered on each side of the fulcrum. But don't try to equate the first class lever to a single cantilever of the entire lever length with the combined load on the end. That is why you got 4 times the moment the first time (8674).
49. ### Levers and UTS

"The original lever I calculated as a resistance of (about) 310N a distance 7mm from the fulcrum with an applied force of 85N a distance of 26mm from the fulcrum." For a second class lever, this is close enough to right. "After this I have multiplied each lengh of the side of the lever by...
50. ### Levers and UTS

Sorry, I tried to rearrange my last post to the end before you posted again. For a first class lever; http://en.wikipedia.org/wiki/Lever The max moment will occur at the fulcrum (not like in second class), so now Mmax=effort*26mm which is the same as the resistance*7mm. Now that you have...