Dive Master mock physics Exams

[BarryNL]

When you have a question that starts at one depth and asks you to solve for another depth, always take it to the surface, then back down.

I find it's always easier to take it into space

Most of the problems are easier if you work in absolute Atmospheres (or bar) and only worry about converting back to depth at the end.

Gas doesn't care whether the pressure comes from water or air and neither should you

 

[Ber Rabbit]

Also, I disagree with Ber, If there is a problem that asks about going from one depth to another, take it to the surface first, then take it back down. Also double check your answers with common sense...if something is deeper, it should compress/if something goes shallower, it should expand.

That said, do what works for you.

Tom

I totally screw up anything physics related so for me that simplistic approach is the easiest way. I had a tutor when I took physics in college (I still failed). He would have me draw the pictures for the problems; I could never get the picture right because what the problem told ME to draw wasn't what it was telling people with a clue to draw.

I have to do the same thing to take it to the surface (where I'm at divided by 1 ata since that's the surface then multiplied by the volume then I would have to do it again, where I'm at -- surface 1ata -- divided by where I'm going then multiply by the volume I calculated earlier) For me that's too many opportunities to screw up a number

Find what works for you and run with it
Ber :lilbunny:

 

[SharkDZ]

Dude,

Don't sweat it. Be prepared and study. I freaked out, but then when I took the exam I did very well. Your studying will pay off. Do not neglect your dive skills, either. And most importantly, have fun!

 

[b1gcountry]

Ber-
It wasn't meant to be a jab at your approach, just another suggestion. My approach works better (for me), and your approach works better (for you).

The reason WHY I like my approach is that you can double check things with common sense along the way. If the volume is 5 at depth, it should be something greater than 5 at the surface (say 10). When you take it back down, it should be something less than 10. If you took it deeper than the original, it will be less than 5.

I didn't have any problem with the physics concepts, and I do the problems "correctly", but I'm dyslexic, and tend to flip the numbers. This just validates I did the math correct (i.e., not 2/3 =1.5)

As to taking the volume into space (0ata), that would give everything an infinite volume using ideal gas laws, so that is definitely not what you want to do (I realize this is not exactly what the poster meant, but want to clarify to anyone taking the post literally)

The two biggest mistakes I've seen on these sort of problems are:
1. Forgetting to factor in the pressure at the surface--33 FSW is at 2ATA, not 1ATA. So you need to divide all your depths by 33ft/10M and the ADD ONE.

2. Getting mixed up about whether to multiply/divide by a certain Atmospheric pressure. I.e., going from 2 to 3 ATA and dividing by 2/3 instead of multiplying by 2/3. Going to the surface first helps this one because you can double check your math with common sense.

Tom

 

[Ber Rabbit]

I didn't have any problem with the physics concepts, and I do the problems "correctly", but I'm dyslexic, and tend to flip the numbers. This just validates I did the math correct (i.e., not 2/3 =1.5)

Cool, we can work together then! You get the physics concept part started and I'll proofread the math I can't even do 5th grade level math story problems, I can work the equations but can't take them from written problems and form them into an equation. I can't even recognize the right equation if you give me a few and tell me to select the right one for the problem. Statistics story problems make perfect sense to me though--go figure.

2. Getting mixed up about whether to multiply/divide by a certain Atmospheric pressure. I.e., going from 2 to 3 ATA and dividing by 2/3 instead of multiplying by 2/3. Going to the surface first helps this one because you can double check your math with common sense.

Tom

That's why I like the word version my husband taught me, I don't have to remember which way the fraction goes. It's always "where you're at divided by where you're going" then multiply by your volume. I just have to get the atmospheres right
Ber :lilbunny: