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Quick Mechanics question

Fronch

Fronch

OCS 03-15 (IW)
Hey, all. I'm taking the ASTB in a few weeks, and I've been studying for a few days now. The only sections I'm concerned about are the Aviation/Nautical Info and the Mechanics sections. For the ANIT, I've made up over 100 flash cards, and I think I'll be fine there. For the Mechanics section, it seems like most of it is basic high school science or common sense, but there are a couple questions I've encountered that trip me up.

Here's one I found on a practice exam, and I have a question about it. I've attached the picture from the problem, which states:

Which one of the following statements is true?

A. If the nut is held stationary and the head turned clockwise, the bolt will move down.
B. If the head of the bolt is held stationary and the nut is turned clockwise, the nut will move down.
C. If the head of the bolt is held stationary and the nut is turned clockwise, the nut will move up.

Here's how I thought about it: Holding the bolt-head stationary and turning the nut clockwise is equivalent to holding the nut stationary and turning the bolt-head counterclockwise. Since counterclockwise is "Lefty Loosey," the bolt-head and nut will move apart, and the nut will move down. However, the listed answer is "C", which I don't really understand.

Is the angle of the threads (tilted down and to the right) in the picture relevant, or is there something wrong with my reasoning? Thanks in advance!
 

Attachments

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    nut-bolt.png
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m26

m26

Well-Known Member
Contributor
edit: totally misread you

I think they're parallel systems, so turning one clockwise is the equivalent of turning the other clockwise. At least that's how it works when I visualize it in my head.
 
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wlawr005

wlawr005

Well-Known Member
pilot
Contributor
The bolt moving down and the nut moving up are the same thing, you're just changing your frame of reference.

Forget the picture, if you logically deduce A is right, the same logic should lead you to the conclusion that B is wrong and C is the same as A.
 
Spekkio

Spekkio

He bowls overhand.
A and C are correct.

Don't get too hung up on errors on the practice tests. The ones sold in book stores aren't proofread very vigorously, but they'll give you good exposure to the types of problems you'll see.
 
Fronch

Fronch

OCS 03-15 (IW)
I'm not worrying too much about it, but there was another nut/bolt question on another practice test I took that I also got wrong, so I'm trying to figure out the source of my misunderstanding.

I guess I'm being really dense on this one... Aren't A and B the ones that are equivalent? Nut stationary and bolt clockwise should be the same as bolt stationary and nut counter-clockwise, correct?
 
wlawr005

wlawr005

Well-Known Member
pilot
Contributor
No. They are spinning the same direction. The bolt moving down is the same as the nut moving up.
 
wlawr005

wlawr005

Well-Known Member
pilot
Contributor
A and C ARE THE SAME THING for the dipicted thread direction. B (and B only) would be correct for the opposite thread direction.
 
Renegade One

Renegade One

Well-Known Member
None
wlawr005 said:
A and C ARE THE SAME THING for the dipicted thread direction. B (and B only) would be correct for the opposite thread direction.
Click to expand...
Spekkio said:
I think you meant B? Righty-loosy for a left-handed screw?
Click to expand...
Pretty sure you should both try again..not that it's critical to national defense, you understand…
A. In this instance, for a reverse-thread bolt, it will move UP.
B. In this instance, for a reverse-thread bolt, the nut will move up.
C. Only correct answer...
 
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