# Shared Flashcard Set

## Details

Lecture 5
Fluids and Solids
27
Physics
07/01/2011

Term
 why are the molecular bonds of a fluid constantly breaking and reforming
Definition
 this is due to the high kinetic energy of the molecule
Term
 the only permanent force a resting fluid can exert is one
Definition
 normal to its surface
Term
 in gas, why does gravity have an insignificant effect on the path of an individual molecule
Definition
 because of the molecules high average velocity
Term
 typically in fluid mechanics, we don't know how much fluid we're dealing with, so we use intrinsic properties like
Definition
 denisty and pressure-analogous to mass and energy
Term
 what is density (in terms and in equation form)
Definition
 the heaviness of a fluid in a specified volume   density=m/V
Term
 for MCAT purposes, how should you think about liquid and solids in terms of denisty
Definition
 a constant density
Term
 what is specific gravity
Definition
 this was created to compare the density of a substance with the density of water
Term
 there are two forms for the density of water that you should memorize, what are they
Definition
 1000kg/m3   1gm/cm3
Term
 what is fluid pressure
Definition
 the average magnitudes of the change in momentum of these collisions divided by the time duration of the collisions and the area over which these collisions occur
Term
 even when there is not an object submerged into liquid,  there is a constant pressure
Definition
 think of this as a measure of the kinetic energy of the random velocities of molecules within a fluid
Term
 what is the eqaution for pressure (pascals)
Definition
 p=F/A
Term
 how can you determine the pressure of a fluid
Definition
 P= (density)(gravity)(depth)
Term
 how does pasacal's principle apply to liquids but not gases
Definition
 pressure applied anywhere to an enclosed imcompressible fluid will be distributed undiminished throughout the fluid.   it does not apply to gas because it is compressible
Term
 what are the two types of motion that molecules of a moving fluid can have
Definition
 random and uniform translational motion
Term
 what type of motion attributes to pressure
Definition
 random translational motion
Term
 idea fluid differs from real fluid in four ways, what are they
Definition
 zero viscosity- meaning that there is no drag, so no opposition to motion   incompressible   lacks turbulence   they experience irrotational flow   All fluids on the MCAT are ideal-remember this
Term
 what is Bernoulli's equation
Definition
 v= SQRT(2gh)
Term
 context: a tank of water has a small spigot   as the velocity of the fluid leaving increases, what happens to pressure
Definition
 it decreases
Term
 where is the greatest velocity of a liquid
Definition
 the middle of the pipe, furthest distance from fluid-object interface
Term
 if the pipe is narrowed, how will this effect viscosity
Definition
 it will increase viscosity
Term
 in order to discuss the elasticity of a solid we must first understand two concepts, what are they
Definition
 strain and stress
Term
 what is stress and what is its equation
Definition
 stress is the force applied to an object divided by the area over which the force is applied   the equation is: F/A and its in N/m2
Term
 what is strain
Definition
 strain is a ratio of change in dimension compared to the original dimension   change of dimension/original dimension
Term
 what is modulus of elasticity
Definition
 this is a ratio that makes stress and strain proportional to each other   stress/strain
Term
 an object will only retain its shape if the stress on the object does not reach higher than
Definition
 the yield point, if it is greater than the yield point, this is what is called a fracture point, and the object will either break or be so strained it will never regain its shape again
Term
 context: solids expand when heated   as their molecules absorb energy, what happens to their vibrations
Definition
 their vibrations need more space, and vibrate faster
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