Before my non pre-med readers tune out from boredom, fellow triathletes please consider how this might be relevant to you.
You might initially inflate your tires to 120psi on a cool 65 degree morning. After arriving at the transition area the temperature is now 80 degrees, which is a 15 degree change from before, thus your pressure has risen to approximately 123psi. After all the time elapsed during your swim, the temperature has increased to 90 degrees, this does not include whether or not your tires have been sitting in the sun during the duration of your swim. This sunlight exposure would further raise the temperature to 110 degrees and your tire pressure would now be at 130psi. At this point the tire that started at 120psi could have exploded, if not then road friction/debris, pavement temperature, and braking could lead to a potentially dangerous blow out.
460 is part of the formula for finding absolute temperature, the rest of the values are inputted into a formula described further below.
(T1) Initial Temp = 65 degrees + 460 = 525 (absolute temperature 1)
(T2) Final Temp = 110 degrees + 460 = 570 (absolute temperature 2)
(P2) Final Pressure is found by solving for P2 in the following: 120/525 = P2/570 (0.228571429 = 0.228571429 * 570 = 130.3psi).
As you know from my About page: 1 year of general physics and lab (1 or 2 sequence) is required for pre-med. It will be helpful to review some basic concepts below before proceeding to the gas laws.
Pressure is force over area
The unit of force is a newton or N
The unit of area (in the metric system) is meters squared or m^2
N / m^2 = 1 pa (one pascal)
Boyle’s Law:
If pressure increases +, volume decreases – or vice versa (at constant temperature)
P = 1/v x C
(C= constant, constant meaning anything that doesn’t change, we assume temperature and the number of molecules stay the same in basic applications)
Avagadro’s Law:
If the number of molecules increases, pressure increases or volume increase (depending on constants)
P = n x C or V = n x C
Gay-Lussac’s law:
If temperature increases, pressure increases
P = T x C
(if volume and the number of molecules is held constant)
Using Guy-Lussac’s Law in relation to the bicycle example (Remember absolute temperature and pressure)
P1 / T1 = P2 / T2
Charles’ Law:
If temperature increases, volume increases.
V = T x C
Check out this great physics gas laws primer:
