Physics Ch. 5

-A liquid or gas
-Unlike a solid, any existing molecular bonds in a fluid are constantly breaking and reforming due to the high kinetic energy of the molecules

-A fluid has only temporal resistance to forces that are not perpendicular to its surface
-Since molecules require room to move, collectively they can create a permanent force outward from within the fluid --> can permanently withstand a force perpendicular to its surface
-the only permanent force is the NORMAL force.

-the 'heaviness' of a fluid, how much mass is contained in its volumes

SI units: kg/m^3

-The density of a substance compared to the density of water

S.G. = dsubstance/dwater

1000 kg/m^3

1 gm/cm^3

-If we take the average magnitude of the force, and divide it by the area over which the collisions are taking place (the surface of the object), we have the pressure experienced by the object.
-Another way to look at fluid pressure: measure of the kinetic energy due to the random velocities of molecules within a fluid distributed over the fluid volume.
-defined as force per unit area:

P = F/A

S.I. unit: Pascal

P = dgy

d = density of fluid
g = gravitational constant
y = depth of fluid

-since fluid pressure is simply weight divided by area, additional fluids on top of the first fluid simply add their weight toward the total pressure

-101,000 Pa

-The pressure applied anywhere to an enclosed compressible fluid will be distributed undiminished throughout the fluid

-A simple machine that works via Pascal's principle.
-Since piston 2 has a greater area than piston 1, the force on piston 2 is proportionally GREATER.
-remember that a simple machine does not change work, thus the distance through which the force is applied is proportionally less.

Fb = d(fluid)Vg

d = density of fluid
V = volume of water displaced
g = gravity

-An upward force acting on a submerged object, and is equal to the weight of the fluid displaced by the submerged object.
-a result of the pressure difference between upper and lower surfaces of a submerged object: since pressure increases with depth, the lower surface of an object experiences more pressure than the upper surface.

-a floating object displaces an amount of water equal to its own weight.
-the submerged fraction of a floating object is equal to the ratio of the density of the fluid in which it is floating.

1. random translational motion that contributes to the fluid pressure as in a fluid at rest
2. uniform translational motion shared equally by all molecules at a given location in a fluid

-motion that is shared equally by all the molecules at a given location in the fluid
-motion of the fluid as a whole
-does NOT contribute to fluid pressure

-motion shared equally bu all molecules at a given location within a fluid
-some random translational motion can be converted to uniform translational motion- if remove a portion of a container holding a fluid at rest, the fluid will move through the opening. Molecules moving at random no longer collide with a barrier, motion is changed into translational motion.

1. No viscosity
2. Incompressible- has uniform density
3. Lacks turbulence- experiences steady (laminar) flow
4. Experience irrotational flow-any object moving with the ideal fluid will not rotate about its axis as it flows.

Q =Av

Q = volume flow rate
A = cross sectional area
v = velocity

P + dgh + 1/2dv^2 = K

K = a constant specific to a fluid in a given situation of flow
P = pressure
d = density
h = distance above some arbitrary point
g = gravity
v = velocity

*equation states that given one continuous ideal flow, the sum of its three terms is a constant at any point in the fluid.
-a restatement of conservation of energy

v = (2gh)^(1/2)

-Real fluids experience drag and viscosity which always act to impede flow. As move away from the fluid-object interface the effect of drag decreases.
-narrowing a pipe through which a nonideal fluid flows will still increase its velocity, but potentially not as much as for an ideal fluid
-the fluid will tend to move from high pressure to low pressure if all other things are equal

-deltaP = QR

R = Resistance to flow
Q = volume flow rate

-The intensity of the intermolecular forces per unit length
-The IMF's pull inward tending to minimize the surface area by creating a more spherical shape, forming a water droplet
-dependent on temp (high temp = low surface tension) and upon the fluid with which it is interfacing.

-The force applied to an object divided by the area over which the force is applied.
-Same units as pressure but as convention we use N/m^2 instead of Pa.

Stress = F/A

-the fractional change in an object's shape.
-A ratio of change in dimension compared to original dimension, has no units.

Strain = delta(dimension)/original dimension

stress = what is done to an object
strain = how the object responds to stress

-Stress and strain are proportional to each other.

modulus of elasticity = stress/strain
-Up to some maximum stress, the modulus of elasticity is constant for a specific substance
-At a certain yield point, the object will remain intact but will not regain its original shape.

1. Young's modulus for (E) tensile stress (compress the object down)
2. Shear modulus (G) for shear stress (the object bends towards a certain direction
3. Bulk Modulus (B) for compression and expansion.

-All forces work in both directions (stretching and compressing)

-for tensile stress
-compressing the object down

-For shear stress
-the object is distorted in a certain direction

-The volume of the object is compressed or expanded.