PHYS Ch. 4 Fluids Flashcards
What is the equation for density?
p = m/v
p (rho) = density, m = mass, v = volume
What is the density of water?
1 g/cm^3 = 1000 kg/m^3
What is the equation for specific gravity?
SG = p/1g/cm^3
What is the equation for pressure?
P = F/A
P = pressure, F = force, A = area
What does 1 Pa equal in Newtons?
1 Pa = 1 N/m^2
What are the units of pressure?
pascals (Pa), millimeters of mercury (mmHg), torr, and atmosphere (atm)
What are the units of density?
kg/m^3
g/mL
g/cm^3
What are the conversions b/w Pa, mmHg, torr, and atm?
1.013 x 10^5 Pa = 760 mmHg = 760 torr = 1 atm
What is absolute/hydrostatic pressure?
the total pressure that is exerted on an object that is submerged in a fluid
What is gauge pressure?
the difference between the absolute and atmospheric pressure
What is the equation of absolute/hydrostatic pressure?
P = Po + pgz
Po = incident/ambient pressure (pressure at the surface)
p = density of the fluid
g = acceleration due to gravity
z = depth of the object
What is the equation for Pascal’s principle of a hydraulic system?
P = F1/A1 = F2/A2
F2 = F1 [A2/A1] or F2 = m*g [A2/A1}^2
A = cross-sectional area, F = force, P = pressure
m = mass in kg, g = gravity (10m/s^2)
What is the equation for Pascal’s principle of volume in a hydraulic system?
V = A1d1 = A2d2
d = d1 [A2/A1]
A = cross-sectional area, d = distance
What happens to force as area increases in a hydraulic system/piston?
the larger the area, the larger the force exerted
What is Archimedes’s principle?
it states that a body wholly or partially immersed in a fluid will be buoyed upward by a force equal to the weight of the fluid that it displaces
When will an object float or sink?
an object will float if its average density is less than the average density of the fluid it is immersed in, and vice versa
What is buoyant force?
buoyant force is the force of a liquid. if 2 objects are placed in a fluid of the same volume, both objects will experience the same magnitude of buoyant force even if the masses of the objects are different
What is the correlation between specific gravity and floating or sinking?
an object with a specific gravity less than or equal to 1 will float in water and vice versa
What is the density of seawater?
1025 kg/m^3
What is the density of an ice cube in water?
0.92 g/cm^3 = 92 specific gravity, which means 92% of its volume is submerged in water and 8% is sitting above the surface
What is the equation for buoyancy?
Fb = mg = pVg
p = density of fluid, v = volume of fluid, g = gravity
m = weight
What is cohesion?
the attractive force that a molecule of liquid feels towards other molecules of the SAME liquid
What is adhesion?
the attractive force that a molecule of liquid feels towards the molecule of another substance
What is the difference between a meniscus and a convex meniscus formation?
a meniscus (curve) forms when the adhesive forces are greater than the cohesive forces. a convex meniscus occurs when the cohesive forces are greater than the adhesive forces
