Defintions and equations Flashcards
Define Displacement
Distance in a given direction
What is the equation for Displacement
s = v x t
displacement = velocity x time
Define velocity
The rate of change of displacement
What is the equation for Velocity
v = Δ s / Δ t
velocity = change in displacement / change in time
Define Acceleration
Rate of change of velocity
What is the equation for Acceleration
a = Δ v / Δ t
acceleration = change in velocity / change in time
Define Current
The rate of flow of Charge
What is the equation for Current
I = Δ Q / Δ t
current = change in charge / change in time
Define the Coulomb
1 Coulomb is the charge that crosses a section of circuit in 1 second when a current of 1 amp flows
Which direction does Conventional Current flow
From positive (+) to negative (-)
Which direction do electrons flow
From negative (-) to positive (+)
What is the equation for current in a material
I = nAve
current = free electron density x cross-sectional area x electron drift velocity x charge
Define Voltage
Voltage is the energy transferred per coulomb of charge (The number of joules transferred per coulomb of charge)
What is the equation for Voltage
V = W / Q
voltage = energy / charge
Define Resistance
The ratio of potential difference to current
What is the equation for Resistance
R = V / I
resistance = voltage / current
Define Ohm’s Law
Provided the temperature is consistent, the Voltage (V) across something is proportional to the Current (I) through it
Define “a negative temperature coefficient of resistance”.
This is when the resistance of a component decreases with temperature
Define “a positive temperature coefficient of resistance”.
When a component’s resistance increases with its temperature
What is the SUVAT equation that links v, u, a and t?
v = u + at
What is the SUVAT equation that links v, u, a and s?
v^2 = u^2 + 2as
What is the SUVAT equation that links s, u, t and a?
s = ut + (1/2)at^2
What is the SUVAT equation that links s, u, v and t?
s = (1/2)(u + v)t
When using SUVAT, what does each letter mean?
S - Displacement, m
U - Initial Velocity, ms^-1
V - Final Velocity, ms^-1
A - Acceleration, ms^-2
T - Time, s
What is the equation that links both graphing intercepts and the gradient?
y = mx + c
Y-Intercept = Gradient(x) + X-Intercept
Define Moment
The force multiplied by the perpendicular distance from line of action of force, to pivot point
What is the equation for Moment?
moment = force x perpendicular distance to pivot
moment = F x d
Define Torque
The rotational motion when two equal forces act in opposite directions
What is the equation for Torque?
torque of a couple = force x perpendicular distance between the forces
t = F x d
Define A Couple
The pair of equal, parallel forces which act in opposite directions to produce rotational motion only
Define Mass
The property of a body which resists change in velocity
Define Weight
The force that acts upon a mass due to a gravitational influence
What is the equation for Weight?
weight = mass x gravitational field strength
w = m x g
Define Equilibrium
When the resultant forces/moment acting on an object are 0 on all axis
Define 1 Newton
The force required to give a mass of 1kg an acceleration of 1ms^-2
What is the secondary equation for calculating the resistance of two objects in parallel?
R(t) = R(1) x R(2) / R(1) + R(2)
Define The Centre of Gravity
The point at which the weight of an object acts
Where is the centre of gravity on a uniform shape?
The centre of the object
Define Coherent
Two or more waves with the same frequency and constant phase difference
Define Unpolarised
Electromagnetic radiation that oscillates in multiple planes at once
Define Polarised
Electromagnetic waves that only oscillate in a single direction
Define Strain Energy
The energy inputted during Plastic Deformation
What is the equation for Strain Energy
W = 1/2 x kx^2 = 1/2 x Fx
Energy = 1/2 x stiffness x extension^2 = 1/2 x force x extension
Define Hooke’s Law
The force is proportional to the extension, up until the elastic limit is reached
What is the equation for Hooke’s Law
F = kx
force = stiffness x extension
What is the alternate equation for Strain Energy
W = 1/2 x Fx
Strain energy = 1/2 x Force x extension
Define Ultimate Tensile Stress
The maximum stress that a material can withstand before failing
What is the equation for Stress
σ = F/CSA
stress = force / cross sectional area
What is the equation for Strain
ε = Δl/l
strain = extension / length
Define Yield Stress
The maximum stress a material can withstand before it begins to plastically deform
Define Stress
Force inputted to deform something
Define Pressure
The amount of force per unit area
What is the equation for Pressure
P = F / A
pressure = force / area
Define Archimedes Principle
The size of the upthrust force is always equal to the weight of the fluid displaced by the object
Define Upthrust
Upthrust is the force that opposes weight when an object is submerged
What is the equation for Upthrust
U = Vgp
upthrust = volume displaced by object x acceleration from gravity x density of fluid
Define Hydrostatic Pressure
Pressure due to a fluid acting on an object
What is the equation for Hydrostatic Pressure
p = hgρ
hydrostatic pressure = height of column x acceleration due to gravity x density of fluid
What is the Crossover Equation
p(1) x V(1) / T(1) = p(2) x V(2) / T(2)
pressure (1) x volume (1) / temperature (1) = pressure (2) x volume (2) / temperature (2)
Define Viscosity
A fluids ability to resist shear forces
What is the equation for Absolute Pressure
Absolute pressure = Gauge pressure + Atmospheric pressure
Define Dynamic Viscosity
The ratio of shear stress to velocity gradient
Define Kinematic Viscosity
The ratio of dynamic velocity to density
What is the equation for Kinematic Viscosity
KV = DV / ρ
kinematic viscosity = dynamic viscosity / density
Define Standard Error
The standard error of the mean is a measure of how accurate your calculated mean is likely to be
What is the equation for Standard Error
Define Fluid Flow due to Pressure Difference
Fluid flows down a pressure gradient
Define A simple machine
Anything that changes the magnitude or the line of action of a force
What is the equation for Mechanical Advantage
MA = oT / iT = oF /iF
mechanical advantage = output teeth / input teeth = output force / input force
What is the equation for Velocity Ratio
VR = iT / oT = oD / iS
velocity ratio = input teeth / output teeth = output rotational speed / input rotational speed
Define Mechanical Advantage
The ratio of the output torque/force to the input torque/force
Define Velocity Ratio
The ratio of rotational speed of the output gear to the rotational speed of the input gear
What is the equation that links Mechanical Advantage and Velocity Ratio
MA = 1 / VR
mechanical advantage = 1 / velocity ratio
What is the equation to combine Velocity Ratios
VR(x) = VR(1) x VR(2)
velocity ratio = velocity ratio (1) x velocity ratio (2)
What is the arrangement for a Class 1 Lever
F(i) —— f —— F(o)
What is the arrangement for a Class 2 Lever
F(i) —— F(o) —— f
What is the arrangement for a Class 3 Lever
f —— F(i) —— F(o)
What’s the rule for remembering the Classes of Lever
F | L | E
1 | 2 | 3
Fulcrum in the middle, Class 1
Lever in the middle, Class 2
Effort in the middle, Class 3
Define Momentum
The product of Mass multiplied by Velocity
What is the equation for Momentum
p = mv
momentum = mass x velocity
What is the rule for Momentum?
Momentum in a collision is always conserved fully
What is Work Done also known as
Energy, in Joules
What is the equation for Work Done
W = Fs
work done = force x displacement
What is the equation for Gravitational Potential Energy
gpe = mgΔh
gravitational potential energy = mass x 9.8 x change in height
What is the equation for Kinetic Energy
Ek = 1/2 mv^2
kinetic energy = 1/2 x mass x velocity^2
What is the definition for Power
The rate at which work is done
What is the equation for Power
P = W/t = ΔE/t
power = work done / time = change in energy / time
What is the equation for Momentum?
p = mv
momentum = mass x velocity
What is the Basic Equation for Completing the square
x^2 + bx = (x + b/2)^2 - (b/2)^2
What’s the Advanced Method to completing the square
ax^2 + bc + c -> a(x + m)^2 + n
where m = b/2a and n = c - b^2/4a
What is the Equation for Frequency Density
frequency density = frequency / class width
What is the Potential Dividers Eqution
Vout = Vin x R / Total
Voltage out = Voltage in x Resistance / Total resistance
What is the equation for Drift Velocity
V = I / nAe
Velocity = Current / Charge carrier density x Cross sectional area x Charge on an electron