Fun with Physics Part 1
Physics…..For many, it is the most intimidating portion of dive theory for your PADI IDC. However, it doesn’t have to be. In this installment of Fun with Physics, we are going to discuss a couple of simple tips and tricks to help simplify physics and we can get more in depth into calculations and equations later on!
Firstly keep in mind at the end of the day it is MATH! It is as simple as following a series of steps to arrive at the correct answer, the trick is understanding which steps to follow and when. Something else to keep in mind while you are preparing is that your exams will provide a table of constants inside the cover so don’t waste your time and energy trying to memorize the following :
- 1 liter of salt water weighs 1.03kg
- 1 liter of fresh water weighs 1kg
- Pressure increases by 1ATM every 10M of salt water
- Pressure increases by 1ATM every 10.3M of fresh water
- Pressure changes per unit of salt water- 0.100 ATM/m
- Pressure changes per unit of fresh water- 0.097 ATM/m
The only constant that is not provided is the fact that there is a 0.6 bar difference in pressure per degree Celsius change in an inflexible container. Now knowing this may give you a feeling of relief but seeing the above numbers might also appear to be overly complicating. Don’t worry it’s easy!
The trick when doing equations is to eliminate any unnecessary or distracting information and focus on what you need to find the answer. For instance, if Bill, Bob and Tom are diving to 23m in the ocean to recover an outboard that weighs 500kg and displaces 300L how much air must be added to a lift bag to bring the outboard to the surface???? Now as much as we love Bill, Bob and Tom they mean nothing in this case! Neither does 23m. The first step is to extract the following information and forget about the rest :
- Environment- Saltwater
- The weight of object- 500kg
- Displacement of object- 300L
Now we can proceed with the above information without any distracting words or numbers to confuse us. Simplify and succeed.
Another trick for the series of exams you will be undertaking is putting the questions into terms you understand. If you are at the point in your diving career that you will be participating in a PADI IDC then you already have a solid understanding of, and passion for diving. For instance, as a dive instructor, there is no need to understand what happens to the gas dissolved in a glass of water when it is placed in a chamber and pressure is increased, I can guarantee you will never come across this situation in your career as a PADI scuba instructor! However it is paramount that you understand what happens to the gas dissolved in divers tissue when they descend and pressure increases……it is the exact same scenario as the glass of water, the only difference? It is put into terms that you understand and are familiar with.
Now, these are just a couple of small tips to make your life easier when taking your instructor exams. Remember just keep it simple! Tune in to the next installment of Fun with Physics for more detailed calculations pertaining to Pressure/Volume relationships and some insight from our good friend Robert Boyle. What is the hardest part of dive physics for you?