Year 1 - A level Flashcards
What are the 7 base units?
Mass - kg Time - s Length - m Current - A Amount of a substance - mol Luminosity intensity - Cd Temperature - K
Pick one of these and turn into base units:
- Force (N)
- Energy (J)
- Power (W)
- Frequency (Hz)
- Change (Q)
- Voltage (V)
- Resistance (Ω)
N - Kg m s-2 J - Kg m2 s-2 W - Kg m2 s-3 Hz - s-1 C - A s V - Kg m2 s-3 A-1 Ω - Kg m2 s-3 A-2
What is the difference between vector and scalar?
Vectors have size and direction, scalars only have size
Formula for velocity?
V = change in displacement/time
Formula for average speed?
S = Total distance/Total time
What are the six SUVAT equations?
- s = ((V+u)/2)t
- V = u + at
- s = ut + 1/2at^2
- s = vt + 1/2vt^2
- V^2 = u^2 + 2as
How do you add vectors?
Place them head to tail.
Pnuemonic for sin, cos and tan?
SOHCAHTOA
What is Newton’s first law?
A body remains at rest or travels at constant speed at a constant velocity in a straight line, unless a resultant force acts upon it.
What is Newton’s second law?
In the presence of a resultant force a body experiences an acceleration.
F = ma.
-A change in direction is a change in V therefore acceleration.
-Stationary or constant speed means no resultant force
-De/acceleration must have an overall force acting.
What is Newton’s third law?
For every force that acts there is an equal force of the same type that acts in the opposite direction.
What are the 10 types of energy?
- Chemical
- Elastic
- Electric(static)
- Electric(current)
- Gravitational
- Nuclear
- Light
- Kinetic
- Sound
- Thermal
What equation links power, force and velocity?
P = Fv
What equation links force, time, mass and velocity?
Ft = mv
What equation links work done (not from rest), mass and velocity?
Work done = 1/2mv^2 - 1/2mu^2
What equation links E.P.E, the spring constant(k) and extension of the material?
E.P.E = 1/2 kx^2
What equation links power, work done and time?
P = WD/t
What equation links momentum, mass and velocity?
P = mv or ΔP = mv - mu(momentum is vector so can have an arrow above it to show direction)
What links force, momentum and time?
F = ΔP/t
What links impulse(Ft), mass and velocity?
What is impulse?
Ft = mΔv
Impulse is a force acting for a given time
What is the centre of gravity?
Centre of gravity of a body is the point at which it’s weight can be considered to act.
What three types of equilibrium are there?
- Stable - returns when slightly displaced
- Unstable - Doesn’t return if slightly displaced
- Neutral - Remains in displaced poistion when displaced slightly
What equation links moments, force and perpendicular distance from pivot?
Moment = Force x Perpendicular distance from pivot
What is a couple?
- Fs + Fs = 2Fs
- Magnitude of each force x separation of their lines of action
- Called torque in engineering
What equation links density, mass and volume?
Density(ρ) = m/v measured in kgm-3
What equation links weight of fluid displays, area, height, density and gravity
W = Ahρg
What equation links pressure, depth, density and g?
P = h ρ g
What are the nine prefixes you need to know?
Terra(T) - x10^12 Giga(G) - x10^9 Mega(M) - x10^6 Kilo(k) - x10^3 Centi(c) - x10^-2 milli(m) - x10^-3 micro(μ) - x10^-6 nano(n) - x10^-9 pico(p) - x10^-12
What is charging by friction?
When you rub two insulators to gain energy as a charge to overcome friction.
What is charging by induction?
When you bring a charged rod, close(not touching) to an object.
(Gold leaf test)
What equation links current, charge and time?
Current(I) = charge flow(Q) / time(t)
What equation links voltage, energy and charge?
Voltage(V) = energy(E) / charge(Q)
What equation links, current, charge carrier density, area, velocity of electron and charge on an electron?
I = nAve
What equation links resistance, voltage and current
R = V/I
What is resistance?
The opposition to the flow of charge
Which way does current flow?
From high to low potential
What is ohm’s law/
Current is directly proportional to voltage(with constant temp.)
-A straight line graph
What is resistance like in metals and how does it change?
- Resistance caused by electrons colliding with each other and lattice
- As temp. increases, ions vibrate faster so more collisions.
What is resistance like in semi-conductors and how does it change? Give 3 examples
- Do not conduct at absolute zero, as temp. increases resistance drops.
- Thermistor - Temp. up = res. down
- LDR - Light up = res. down
- Diode - pd > 0.6v = res. down
What is resistance like in superconductors and how does it change?
- At very low temp. (near 0K) resistance drops rapidly, therefore, current seems to flow forever once started.
- Large currents can pass with minimal energy lost to heat.
What equation links electrical WD, Current, time and voltage?
Electrical WD = current x time x voltage
What is power? What equation links power, energy, time?
Power is rate of doing work
- Power = Energy(WD) / time
What equation links, resistivity, resistance, length of conductor and area?
R = (ρ x L) / A
-Reisistivity measured in ohm-meters (Ωm)
What is Kirchoff’s first law?
The conservation of charge.
-ΣI in junction = 0
What is Kirchoff’s second law?
The conservation of energy(voltage)
-ΣEMF’s = ΣVs
What is the ratio of: -Voltage in series
- Current in series
- Resistance in series
V total = V1 + V2 + V3
I total = I1 = I2 = I3
R total = R1 + R2 + R3
What is the ratio of: -Voltage in parallel
- Current in parallel
- Resistance in parallel
V total = V1 = V2 = V3
I total = I1 + I2 + I3
1/R total = 1/R1 + 1/R2 + 1/R3
What should you not do when R = V/I
Do not mix total V’s, R’s and I’s with component ones
What is the difference between potential against P.d.?
Potential is the voltage at one point.
Potential difference is the voltage change between two points.
What links V1, Vt, R1 and Rt?
V1 = Vt x (R1/Rt) V2 = Vt x (R1/Rt) V/Vt = R/Rt
What is EMF?
Electromotive force is the volts converted by the power source into electrical energy.
What is potential difference?
P.d. = between two points is WD or electrical energy per unit charge converted to other forms of energy.
What links EMF, Current, Resistance and internal resistance?
EMF = IR + Ir
Benefits of combining cells in parallel or series?
Series: Bigger EMF
Parallel: Lower internal r, Higher I, longer life
What is frequency?
The number of complete oscillations(cycle) per second - f(Hz)
What is period?
Time for one complete oscillation - T(s)
What is amplitude?
Maximum displacement of an oscillation from the equilibrium (midpoint) position - A(m)
What is wavelength?
Distance between consecutive points in an oscillation which are in a phase - λ(m)
What is wave speed?
V = frequency x wavelength (V = f x λ)
What are the three categories of waves?
- Progressive vs stationary
- Longitudinal vs transverse
- Mechanical vs electromagnetic
What is the difference between progressive and stationary waves?
Progressive transfer energy or information without transferring matter.
Stationary don’t transfer waves
What is the difference between longitudinal and transverse?
Longitudinal have particle oscillations are parallel to the direction of travel(propagation) of the wave.
Transverse have particle oscillations are perpendicular to the propagation of the wave.
What is the difference between mechanical and EM?
Mechanical need a medium to travel.
Electromagnetic do not need a medium to travel.
What does a full cycle represent in a) displacement - distance graph
b) displacement - time graph
a) λ - wavelength
b) T - time period
What is it called when the particles of waves are:
a) closer together
b) further apart
a) Compression
b) Rarefaction
What is stoke’s law?
F = 6 π η r v
- Only works for small spherical objects at slow speeds
- As temp increases viscous drag(F) decreases in a liquid but increases in a gas
What is laminar flow?
A flow pattern, where all parts of the fluid, flow in the same direction
What is turbulent flow?
A flow pattern, where layers in the fluid get mixed up. It increases drag.
What action does viscous drag act in? And when is it present?
The opposite to motion. It is greater than turbulent or laminar flow and is present when a solid moves through a liquid.
What is the equation for a ball falling through a liquid.
- Upthrust + stoke’s F = weight
- U + F = W
- 4/3 π r^3 p_f g + 6 π η r v = 4/3 π r^3 p_s g
- η = 2/9 x (r^2 g (p_s - p_f)) / v
What is breaking stress(or ultimate tensile stress)?
The maximum tensile stress that produces fracture
What is density equation?
Mass / volume
What is elastic limit?
The maximum force a body can endure and still regain its original shape and size, when a force is removed.
What is elasticity?
The property a material has whereby it regains its original shape and size when a deforming force is removed.
What is Hooke’s law?
The extension of a stretched spring(or wire) is directly proportional to the extending force, provided the limit of proportionality is not exceeded.
F = kx with k as spring constant
What is stiffness?
The stiffness of a body is the measure of its resistance to changes in size/shape.
What is strain equation using extension and original length ?
Ɛ = x / original length
What is equation for stress using force and area?
σ = F / A.
Units of stress are Nm-1(Pa)
What is toughness?
Ability to absorb energy from impacts and shocks without breaking.
What is yield point?
For a body being extended by an applied force, the yield point is when a large extension is produced for a very small increase in force. The material of the body is said to show ‘plastic’ behaviour.
What is creep?
Creep occurs when a material is under constant stress over time. Strain gradually increases, causing eventual fracture.
What is the formula for speed of wave on a string?
V = √T/u
T: Tension(N)
U: Mass per unit length
What is the phase difference for a waves in phase and a waves out of phase
In phase: 360° or 2 π
Out of phase: 180° or π
What is the path difference for centre bright and 1st dark fringes?
Centre Bright fringe: 0, in phase
First bright fringe: 1 wavelength
Dark fringe: 1/2 wavelength , phase difference 180°
What is diffraction?
The spreading out of waves as they pass through a gap or around an obstacle. Best diffraction when gap smaller than or equal to wavelength
What is necessary for interference?
- Coherence - constant phase difference
- Vibrations/ overlapping
- Same type of wave/ similar amplitude
What is the formula linking fringe separation, wavelength, distance from slit and slit width?
Fringe sep. = (wavelength x D) / d
What equation links order, wavelength, slit separation and angle from centre point?
n λ = d sin(angle)
What angle is the max number of fringes at?
When sin(angle) = 1
What is Young’s modulus?
E = σ / Ɛ measured in Pa
Equation for elastic strain energy with spring constant and extension?
E(el) = 1/2 Kx^2
Can be found as area under force-extension graph.
Equation for force using spring constant and extension?
F = k x
Equation linking intensity of radiation, power and area?
Intensity of radiation = Power/Area
What is critical angle formula?
Sin C = 1/n
What is the interface between two mediums equation?
n1sinθ1 = n2sinθ2
What is plane polarisation?
Only transverse waves can be polarised. It is to create waves in one plane by sending them through grating
What is refractive index in terms of velocity in substance
N = V vacuum/ V substance
What is true about an elastic collision?
Both energy and momentum are conserved
What is true for an inelastic collision?
Only momentum is conserved. Lost energy goes to heat. Perfectly inelastic = object sticks
What is resolution?
When two points are seen as separate - must be at least one unstimulated pixel between them
How can you increase resolution?
Higher frequency and shorter wavelength pulses. Means more resolution but shorter depth
When is sufficient resolution?
Wavelength less than half the size of object scanned
What is the equation linking power of lens and focal point?
Power of lens = 1/f
Units: m-1
Equation for power of combined lenses?
Power of a combination of lenses = P1 + P2 + P3
What equation links distance between object to lens(u), distance between image to lens(v) and focal length?
1/u + 1/v = 1/f
What is the equation for magnification?
Magnification = image height/ object height
What is different about u, v and f in convex and concave lenses?
Convex: u and f are +: but v is only + if u > f
Concave: f and v are -
What are the two types of fibres?
- Multimode
2. Monomode
What is the speed of light used in calculations?
3x10^8 ms-1
What links momentum, planks constant and wavelength
Momentum = planks/ wavelength
What links energy, mass, specific heat capacity and temp.
E = mc x change in T
What links energy, mass and specific latent heat
Energy = mL
What’s the link between energy of a photon, planks and frequency
E = hf
What’s threshold frequency?
The minimum energy required by an election to leave the metal’s surface
What is true about Ke at threshold?
Ke = 0 and f = work function / h
