Mr mcintyre Flashcards
what is the density equation
density = mass
————
volume
how to determine the density of a liquid
-place a container of a given volume on a scale and find its mass
-fill the container with the liquid and find the new mass
- minus the mass of container from mass of container + liquid
-mass / volume = density!
what is upthrust
upward force applied to an object by the fluid its immersed in
what is Archimedes principle
upthrust = weight of fluid displaced
what’s the equation for upthrust
U(f) = ρ(f) x V(f) x g (f) = of fluid
v = volume
U = upthrust
U(f) = ρ(f) x 3/4πr^3 x g
how to prove an object is floating due to Archimedes principle
- U(f) = w(o)
- ρ(f) x V(f) x g = ρ(o) x V(o) x g
- ρ(f) x V(f) = ρ(o) x V(o)
U = upthrust g = gravity
ρ = density (f) = of fluid
V = volume (o) = of object
what does it mean if an object is floating
its density will be less than that of the fluid but its volume will be greater
if an object is just submerged what does this mean using Archimedes principle
ρ(f) = ρ(o) or ρ(f) x V x g = ρ(o) x v x g
the density of the fluid and object are the same
what is laminar flow
flow in one direction with parallel and constant streamlines
what is turbulent flow
streamlines cross and eddy currents are created, they are constantly changing
when does laminar flow occur
the rate of flow is BELOW a critical value
when does turbulent flow occur
the rate of flow is ABOVE a critical value
or
an object moving through a liquid
what is viscosity
the internal friction between layers of a liquid which resists the flow
what is stokes law
F = 6πηrv
F = drag
η = viscosity coefficient
r = radius of ball bearing
v = velocity of ball bearing
what are the requirements of stokes law
object must be solid smooth and spherical , object must be uniform density , object must be >0.001 compared to fluid molecules , must be laminar flow , fluid must be homogenous
What is Hooke’s law
Force =hooke’s constant x change in length
What does hooke’s law show
That the change in length is directly proportional to the force applied until it reaches the limit of proportionality
What does the area under a force, extension graph equal
Work done
What is stress
Force per unit of cross sectional area
What is the equation for stress
Force
—————————-
Cross sectional area
What is tensile stress
Stress of stretching something
What is compressive stress
The stress caused by pushing things together
What is the equation for strain
Change in length
————————
Original length
What are the components on a stress strain curve
From point of occurrence
- proportional limit
- Elastic limit
- Yield point
- ultimate strength
- rupture strength
What is the limit of proportionality
last point where hooke’s law applies and the stress to strain is directly proportional
What is the elastic limit
the point where the material will no longer return to its original shape
What is the yield point
the point where the material begins to visibly deform plastically
What is the ultimate strength
the material has reached its max capability to resist stress before breaking
What is rupture strength
The material fractures and loses all capability to resist stress
How to calculate work done in a force extension graph
Work done = 1/2 (force x extension)
How to substitute F = ke into E = 1/2Fe
E = 1/2 ke^2
What is the equation for Young’s modulus
Stress. F x L
———. =. ————-
Strain. A x ΔL
What property of a material does Young’s modulus describe
A materials stiffness
What is stiffness
The extent a material resists deformation in response to an applied force
What is Young’s modulus on a stress strain graph
The gradient
what is the equation for charge
ΔQ
I = —–
Δt
what is the equation for kirchoffs first law
I1 = I2 + I3
what is the equation for kirchoffs first law
total current into a junction = total current out of a junction
what is EMF
The energy provided to the circuit by the cell to do work in the circuit
what type of energy is provided to an electron by a cell
electrical potential energy
what happens when an electron passes through a lamp
the electron does work and loses its potential energy, charge is not “used up”
what does a cell with a higher EMF mean
a greater change of potential energy is provided by the cell
what is a “volt”
the energy transfer per coulomb of charge as charges move between 2 points on a circuit
what is kirchoffs second law
in any loop around the circuit, sum of the EMF’s = sum of PD’s
what is ohm’s law
for a resistor at a constant temp, PD is directly proportional to the current (V = IR)
what is resistance
the ratio of potential difference across component to current through it
what is an ohmic resistor
the more current the more voltage if resistance remains constant
what is a potential divider
2 or more resistors in series
fixed PD between them
source PD is divided between resistors
how to find the current in a circuit with a potential divider
R0 = R1 + R2
V = IR
I = V / R
v ----------- = I0 R1 + R2
how can you find the voltage over a single resistor in a potential divider
V0 x R1
———– = V1
R1 + R2
what is the relationship between voltage and resistance in a potential divider
V1 R1
—- = —-
V2 R2
what is a material “resistivity”
its opposition to the flow of electrons
what is resistance directly proportional to
Length
resistivity
what is resistance inversely proportional to
cross sectional area
