TheDude86
New Member
There were a couple of "WTF" questions. Those, however, had to do with aeronautical terminology, which is something I have no experience with and could have used more preparation. I took the test in the later part of September. The mathematical and mechanical sections aren't super hard, in fact they're easy. What makes it difficult is the pressure of very limited time. That is the point of the test though. Think of it more as a stress test than anything else. If you practice basic arithmetic, geometry, and algebra to the point of intuition you'll be more than fine with the math section. As far as the mechanical section goes, you'll be looking at the basic principles of gears, pulleys, levers, forces, and some electromagnetic principles (however I only encountered a couple questions involving electricity). Most of the info I'm about to write down you can find online, or in one of the study books (arco or barron's). This is the material I do remember encountering though.
When it comes to gears, or belt fed rotational devices, remember that the smaller the diameter (or radius, however you want to look at it) the faster it will rotate NO MATTER WHAT. They will try to trick you by adding a bunch of fluff into the question, don't let the "X rotates this many times and Y rotates this many times, which rotates faster" fool you. The smaller one rotates faster.
- You'll be asked to find the number of rotations of one gear given the number of rotations of the gear it is meshed with. Remember the equation: R1 = (D2xR2)/D1 where:
R1 is the number of rotations you're solving for
R2 is the known number of rotations for the second gear
D1 is the number of teeth on the gear you're solving for
D2 is the number of teeth on the second gear (known gear)
- Consecutive meshed gears will always rotate opposite of each other. Therefore gears 1,3,5 etc. will rotate in the same direction and gears 2,4,6 etc. will rotate in the same direction but opposite of the odd numbered gears. This will help when they ask which direction what gear rotates.
-The gear ratio with the highest mechanical advantage is whatever answer gives a ration of highest to smallest. By example:
"Which gear ratio provides the highest mechanical advantage?"
A. 14:8
B. 16:12
C. 27:9
The answer would be C.
-Ummm, what else. Oh yeah, belt fed rotating devices will rotate in the same direction if the belt is not crossed and will rotate in opposite directions if the belt is crossed.
- I don't remember any electrical equations off the top of my head, but I don't remember needing them. The questions involving electricity and magnetism were very simple in nature, from what I can recall.
-Know the difference between a first, second, and third class lever.
-Uhhh, when it comes to hydraulic pumps or jacks. They'll question you on the distance one jack would travel if you applied a force to the other. For this remember the equation: A2/A1 = D1/D2 where:
A1 is the area of the smaller cylinder
A2 is the area of the larger cylinder
D1 is the vertical distance moved by the smaller cylinder
D2 is the vertical distance moved by the larger cylinder.
Example: "If the smaller cylinder is two inches in diameter and the larger is 8, by how much will the smaller cylinder rise if the larger is compressed by one inch?"
The answer is 4. This is also the mechanical advantage
-One thing to remember about mechanical advantage: you can increase the mechanical advantage by changing the makeup of whatever system you're using. (That is, adding pulleys, enlarging gears, changing the area of a pump)This may make the task seem easier to accomplish. However, no matter what you do, in a perfect system you will still have to do the same amount of work to achieve the same results. In an imperfect (real) system it can make things worse.
-Pulleys are a great example of this. (this is definitely material they questioned me on) If you have to lift mass x up a distance of y feet with only one cable around a pulley, you'll have to exert the full amount of force to lift mass x. If you suspend mass x with a two cable system then you will only have to exert a force equal to half the weight but pull the cable twice as far. Hence, you are doing the same amount of work. If you change it again to a 3 cable system, then the force will be 1/3 the weight and you will pull 3 times as far.
-Force is also a big one, but not necessarily in computing answers for equations. You'll be asked quite a bit about what direction the force of lift is asking, or what direction friction is acting upon an object. You'll also be asked about the different "components" of force (the downward an diagonal components of gravity acting on a cart rolling down a hill for instance).
Thats most of what I can remember off the top of my head in relation to the mechanical section. The gouges the ORs give are helpful, but I think the study books are more beneficial mainly because the mathematical and physical questions you'll come across in those books are more difficult than the questions on the actual ASTB. I have the Barron's which I like and probably should have studied more. One word of caution though. Many posters here have found errors in the books. I found a couple scattered in the practice tests. The information and difficulty of most questions, in general, is very beneficial though.
Lastly, from my point of view, and as everyone else here has noted, time management is important. As I said earlier, think of this as a stress test more than anything else. Keeping calm is key, especially when you run up against a question that stumps you. Take a couple seconds to think it out and if you still can not find the answer, mark the question or make an educated guess and don't sweat it. Go back if you have time. As Rass pointed out (By the way, great score Rass!) Being quick with the calculations is key. Practice the equations until they become intuitive so your mind can become familiar with the patterns. It's just like practicing anything else (sports, art, music, etc), you want the process to become fluent so your mind doesn't have to crunch the numbers when you need it thinking about other stuff. (If I could only learn to follow my own advice!!!)
Sorry for the long post. Hopefully this will help.
