MCAT Tutorial: Hydrostatics

|dw:1563595410252:dw| probably my weakest mcat physics section so I'm writing this to help myself just as much as I want to help others

\({\bf{Density:}}\)
density = mass/volume
density of water (memorize these): **1000kg/m^3, 1 g/cm^3, 1kg/L **
**specific gravity** = density of a substance/density of water
you can multiply a substance's sp. gr. by 1000 to get the density in kg/m^3 (SI units) and convert from there as needed

\({\bf{Pressure:}}\) general formula = Force/Area gauge pressure = the pressure on an object solely due to the fluid it is in. this # doesn't take into account atmospheric pressure. = ρ_fluid * g * D where ρ_fluid is the density of the fluid (not the object), g is the gravitational constant, D is the depth of the object if you want total pressure, simply add atm pressure to this quantity, or in the case of a smaller system, you'd add the "surface pressure" (a.k.a the pressure caused by the fluids above the surface)

\({\bf{Archimedes' Principle:}}\)
**F_buoyant = weight of the displaced fluid
F_b = ρ_fluid * V_sub * g**
where ρ_fluid is the density of the fluid, V_sub is the volume of the object that is submerged, g is the gravitational constant
don't get this confused w/ the pressure formula, which uses depth not volume, and measures a different quantity
for a floating object (a.k.a object w/ density lower than the fluid density), **the weight of the object is equal to the buoyant force** and **the portion of a floating object that is submerged = the density of the object/ density of the fluid**

\({\bf{Pascal's~Principle~and~Surface~Tension:}}\) consider a hydraulic press: |dw:1563598416258:dw| with an input surface (left) and an output surface (right) F1/A1 = F2/A2 exerting a force on a small area greatly multiples the pressure. if the output surface has a larger area than the input surface, the output force will be greater than the input force *special note* when you're doing the calculations for a situation like this, be wary if they give you diameters/radii instead of A --> remember to square the ratio of linear distances to get the ratio of areas. guarantee they'll try to trip you up on this. There's not a lot of problems on surface tension but just remember [b/the force of surface tension = 2γL where γis the coefficient of surface tension[/b]

Source material is Chapter 8.1 of MCAT: Physics and Math Review, 3rd edition by Princeton Review