Physics is notoriously hard, but knowing the bases makes building up to complex ideas a lot easier. Here you’ll find a mix of variables and vocabulary.
We’ve arranged the table below by topic, for your convenience! And here is our recommended data booklet.
| Topic | Definition | Equation |
| (1) Physical Quantities Units & Measurement Techniques | ||
| Powers of Ten |
|
|
| 7 Base Units |
|
|
| Scalar Quantity | Physical quantity that has magnitude only |
If x=a +b or x=a-b Δx = Δa+ Δb |
| Vector Quantity | Physical quantity that has magnitude and direction |
If x=ab or x=a/b Δx/x= Δa/a+ Δb/b If x=an where n= is any number Δx/x= n (Δa/a) |
| Random Error | Causes reading to be scattered (equally) about the true values. | |
| Systematic Error | Shifts all readings away from the true value in one direction. | |
| (2) Kinematics | ||
| Displacement | Distance travelled from a fixed point/origin in a stated or specific direction. |
S=ut + ½at Where S= Displacement (m) U= Initial Velocity (ms-1) T= Time (s) A= Acceleration (ms-2) V= Final Velocity (ms-1) |
| Velocity | Rate of change of displacement |
V2 = u2 + 2as Average speed= <v>= (u+v)/2 |
| Acceleration | Rate of change of velocity |
A=(v-u)/t Assumption: Acceleration is a constant motion in a straight line. |
| (3) Dynamics | ||
| Resultant Force | The resultant force is equal to the rate of change of momentum. (Newton’s 2nd Law) |
F=ma F= Resultant force (N) M= Mass (kg) A= Acceleration (ms-2) F= (mv)/t |
| Momentum Impulse | The product of mass and velocity The product of Resultant Force and the rate of change of time. |
P=mv P= momentum (kg ms-1) Impulse= F Δt |
| Conservation of Momentum | Total momentum of an isolated system is constant where no resultant force acts. Thus, momentum before is equal to momentum after in both x- and y- directions. |
For elastic collision, Relative speed of approach = Relative speed of separation U1-U2=V2-V1 |
| (4) Forces | ||
| Mass | Measure of a body’s inertia/resistance to change to motion. | |
| Weight | The effect of gravitational field on a mass. |
W=mg M= mass (kg) G= gravitational field of free fall on earth 9.81ms2 |
| Moment of a force | The product of force and perpendicular distance from line of action of force to pivot. |
Moment of a force= Fd F= Force (N) D= Distance from the pivot/fulcrum (m) |
| Couple | Pair of forces, not in line with each other but equal in magnitude but opposite in direction. | |
| Torque of a Couple | Product of one of the forces and the perpendicular distance between the two forces. | |
| Principle of moments | For equilibrium, sum of clockwise moments about a pivot is equal to the sum of anti-clockwise moments about the same point. | |
| Equilibrium | Resultant force about any direction is equal to zero and resultant moment about any point is equal to zero. | |
| Centre of Gravity | A point where all the weight of the body may be considered to act. | |
| (5) Work, Energy, Power | ||
| Work done | It is the product of force and the distance moved in the direction of the force. |
W=Fa W= Work done (J) F=Force (N) A= Acceleration (ms-2) Work done by gas: p ΔV P= pressure (Pa) ΔV= Change in volume (m3) |
| Joule, J | When force of 1 N moves a body a distance of 1 m in the direction of force, the unit of work done is joule. | |
| Gravitational Potential energy | Energy stored due to the position of mass in the gravitational field. |
gpe= mGh m = mass (kg) G= gravitational field strength (9.81 ms-2) h= height (m) |
| Elastic Potential energy | Energy stored due to deformation of a body. Ex. Work is done to compress the spring |
Elastic PE= ½ kx2 Elastic PE= ½ Fx Where k=spring constant (kg s-2) x= extension (m) F= Force (N) |
| Electric Potential energy | Energy stored due to position of charge in the electric field. |
Electric PE= q ΔV Where q= charge of particle (C) ΔV= potential difference (V) |
| Potential Energy | The ability to do work due to a body’s position or shape. | |
| Kinetic Energy | The ability to do work due to motion of a body. | |
| Internal Energy | Sum of random distribution of kinetic and potential energies of atoms/molecules. | U= Ek+Ep |
| Principle of conservation of energy | Energy can neither be created nor destroyed, it is only converted from one form into another. | |
| Power | Rate at which work is done. |
P= Fv = work done/time F=Force (N) v=Velocity (ms-1)
|
| Efficiency | Useful Output/ input x (100%) | |
| (6) Density and pressure | ||
| Density | Mass per unit volume |
Density = ρ ρ=m/v M= mass (kg) V= volume (m3) |
| Pressure | Force per unit cross-sectional area | P=F/A |
| Buoyancy/Upthrust | Force which is due to the difference of pressure at the top and bottom surfaces of the object immersed in the fluid. |
Pressure due to liquid column, P=ρgv Where: P= Pressure (Pa) g= gravitational field strength (ms-2) ρ= Density (kgm-3) V= Volume displaced (m3) |
| Archimedes’ Principle | The upthrust on an object immersed in a liquid is equal to the weight of the liquid displaced by that object. |
Total pressure at depth x Ptotal= Patm+ Pressure due to liquid column |
| (7) Deformation | ||
| Stress | Applied force per unit cross sectional area. |
σ=F/A Where: F= Force (N) A= Cross-sectional area (m2) |
| Strain | Ratio of extension to original length. |
ε=e/L Where ε = Strain e= extension L= Original Length |
| Young Modulus | Ratio of stress to strain | E= σ/ ε |
| Ductile | The material changes shape rather than cracking when subjected to a large and steady applied force. It can be permanently stretched. |
Hooke’s Law F=ke K= spring constant (kg s-2) e= extension (m) |
| Elastic | The material will return to its original length/shape when the applied force/weight/load is removed. |
Springs in series: Ktotal= (1/k1+1/k2+1/k3)1 Springs in parallel: Ktotal= k1+k2+k3 |
| Plastic | The material does not return to its original length once the applied force is removed and is permanently deformed. | |
| Elastic Limit | The point beyond which the material does not return to its original length when the applied force/load is removed. | |
| Ultimate tensile strength | Maximum force per original cross-sectional area which the wire can handle before breaking. | |
| Hooke’s Law | Within the limit of proportionality, extension is proportional to force applied. | |
| (8) Electric field, current & D.C circuit | ||
| Electric Field | A region of space where a charge experiences a force. | |
| Electric Field strength | Force per unit positive charge. |
Electric Force F=qE Where q= Charge E= Electric field strength |
| Current, I | Rate of flow of charged particles |
I=nAvq Where n=number density, I.e the number of conduction electrons per unit volume. A= cross sectional area (m2) v= mean drift velocity of the electrons (ms-1)) q= charge of each particle (C) |
| Coulomb, C | When current of 1A flows through a point in the circuit for 1s, the unit of charge is coulomb. |
Q=It or Q=Ne I= current(A) t= time (s) N= number of electrons e= Charge of electrons |
| Potential difference | The energy transfer from electrical to heat energy and other forms when a unit charge moves across a component. | Electric potential energy= qΔV |
| Electromotive force | The energy transfer from chemical to electrical energy by the source when a unit of charge moves round the complete circuit. | Electromotive force= Potential Energy/ charge |
| Volt | When energy of 1 joule is converted when charge of 1 coulomb passes through one point to another, the unit of potential difference is volt. | |
| Power | Rate at which work is done/ rate of energy transfer. |
Power=energy/time P= IV P= I2R P=V2/R Where I= current (A) R= Resistance (Ohm) V= Potential difference or Electromotive Force (V) |
| Resistance | Ratio of potential difference to current. |
Resistance= pL/A Where p= density (kg m-3) L=length of the conducting object (m) A= Cross-sectional area (m2) |
| Ohm | When potential difference across a component is 1 volt and current flowing through is 1 ampere, the unit of resistance is Ohm. |
Ohm’s law, V=IR For potential divider: where in series, current is the same at all points. So, V/R= constant. i.e. V1/R1=V2/R2=Vtotal/Rtotal |
| Internal resistance | The resistance between terminals of power supplies causing some electrical energy to be dissipated in the power supply itself. |
With internal resistance r, Emf E= IR = Ir |
| Kirchhoff’s 1st law | At a junction, sum of currents entering in the junction is equal to the sum of currents leaving the junction. |
I1+I2=I3+I4 |
| Kirchhoff’s 2nd law | In a closed loop, the sum of electromotive forces is equal to the sum of the potential differences. | E1+E2=V1+V2 For Potential divider |
| (9) Waves, Superposition & Standing waves | ||
| Transverse waves | Wave particles oscillate perpendicular (or normal) to the direction of energy transfer of wave. |
Equation of wave: V=fλ Frequency, f= 1/T |
| Longitudinal waves | Wave particles oscillate parallel (or along) the direction of energy transfer of wave. | |
| Displacement | Distance from the equilibrium position | |
| Amplitude | The maximum displacement of a particle in the wave (from equilibrium position) | |
| Wavelength,λ | The distance between two successive points of the same phase/ between 2 successive peaks/ troughs | |
| Period, T | Time taken for one complete wave to be generated/ for a particle in the wave to complete one cycle. | |
| Frequency, f | The number of complete waves produced per unit time by the source. | |
| Intensity, I | Power incident per unit area (inclined perpendicularly to the wave’s velocity) |
I= Power/Area I α A2 α 1/r2 |
| Principle of superposition | When two waves meet at a point, the resultant displacement is equal to the vector sum of individual displacements of the waves at that point. | |
| Diffraction | The bending or spreading of waves into geometrical shadows as it passes through an aperture/ round an edge, | |
| Coherent | Constant phase difference between two waves at all times. |
To find phase difference α /360°= α/2π=x/λ=t/T |
| Interference | When two or more coherent waves meet at a point, there’s a change in overall intensity/ displacement resulting in regions of maximum and minimum intensities. |
Double slit Λ= ax/D Diffraction grating= nλ=dsin α |
| Progressive waves | Waves transfers enters energy (from one point to another). | |
| Stationary waves | Energy is trapped between boundaries. | |
| Antinode | Point where maximum amplitude of vibration occurs. | |
| Node | Point where no vibration occurs/ zero displacement. | |
| Doppler effect | The observed frequency is different to the emitted frequency when there is relative motion between the source and the observer. Note: actual frequency of sound emitted by the source =fs Vs= speed of moving source and v=speed of waves travelling through air |
F0=fsxV/(V + – Vs) Where + applies to receding source and – applies to approaching source. Where f0= Frequency observed fs= Source of frequency V= Velocity of wave Vs= The source’s velocity |
| (10) Nuclear Physics | ||
| Isotopes | Elements of the same atomic number, and with the same number of electrons, but having a different number of neutrons. | |
| Radioactive decay | Process by which unstable nuclei become more stable by emitting alpha or beta particles and/or gamma rays. |
N=N0exp(-lambda t) Where N= Number of undecayed nuclei N0 = Initial number of undecayed nuclei Lambda= Decay constant (s-1) t= time (s) |
| Spontaneous | The rate of decay/ count rate is unaffected by environmental changes such as temperature and pressure | |
| Random | It is constant probability of decay per unit time of a nucleus where one cannot predict which particular nucleus will decay next | |
| State 2 observations of Rutherford alpha-scattering experiment: | 1) Most of the a-particles pass straight through the gold foil without being deflected. 2) Some a-particles are scattered through larger angles, a few were scattered more than 90°. | |
| Explain the above observations of Rutherford alpha-scattering experiment: |
1) Atom is mainly empty spaces as the volume of the nucleus is very very small compared to the volume of the atom 2) Nucleus must be positively charged and dense/massive. |
|
| State what are conserved in all nuclear reactions: | 1) Proton number 2) Mass-energy/ momentum 3) Nucleon number/ number of neutrons. |
In all nuclear reactions (and decays), mass-energy is conserved, i.e. E= mc2 The loss or difference in mass (on right-hand side of equation) is the energy released in the equation. |
| Activity | Activity is the number of nuclear decays produced per unit time by the source (in all directions) |
A=lambda N Where A= Activity Lambda= Decay constant N= Total number of nuclei in source A=A0exp(-lambda t) |
| Count rate | Count rate is the number of decays detected by a detector per unit time. | |
| Half-life t1/2 | It is the time taken for the number of radioactive nuclei to decrease/ reduce to half the initial or original number. | |
| Decay constant | It is the probability of decay of a nucleus per unit time. | Lambda t1/2=ln2 |
| Mole | Amount of substance containing the same number of particles as in 0.0012kg of carbon-12. | |
| Avogadro’s constant | Number of carbon-12 atoms in 0.0012kg (or 12g) of carbon 12. | |
| Binding energy of a nucleus | Binding energy is the energy needed to separate (all) the nucleons in the nucleus to infinity (referring to very long distance). | |
| Fission | The splitting of a heavy nucleus into two lighter nuclei of approximately equal mass. | |
| Fusion | When (two) light nuclei combine/join together to make a heavier (more stable) nucleus. | Nuclear fusion releases more energy per nucleon than nuclear fission. This is because the Binding-Energy per nucleon verses nucleon number graph is steeper where fusion occurs than where fission occurs. |
| 11) Motion in a circle | ||
| Uniform circular motion | Is defined as motion of a body in a curved path at constant speed due to a perpendicular force acting on the body. | |
| Angular displacement (θ) | Is defined as the directed angle with respect to the centre of the arc travel. (It is measured in radians) |
Arc length s=r θ Where θ= angular displacement r= radius |
| Angular Velocity | Is defined as the rate of change in angular displacement (or the angle swept out by the radius per unit time). |
Ω=2π/T Ω=2πf Where Ω= angular velocity T= Period (s) f= Frequency (Hz) V=r Ω Where V= Linear velocity (ms-1) r=radius (m) |
| Centripetal force | Is a resultant perpendicular force that acts toward the centre of the circle to keep a body moving in uniform circular motion. |
Fc=m(v2/r) = mΩ2r = mvΩ Reminder: F=ma Therefore, Centripetal accelaration a= vΩ or Ω2r or v2/r |
| Weightlessness | A sensation experienced by an individual when there are no external objects touching one’s body and exerting a push or pull motion. | |
| Weightless | The sensations exist when all contact forces are removed. | |
| 12) Oscillations | ||
| Oscillation | Is defined as to and fro motion within two limits. For a system to oscillate, the system must have: 1) a mass 2) an equilibrium position where the resultant force acting on the mass is zero 3) A restoring force which acts to return the mass to the equilibrium position where the mass is displaced. |
F directly proportional to –x In an oscillating system, the restoring force acting on the mass: 1) has a direction that is always towards the central equilibrium position 2) has a magnitude that is proportional to the displacement of the mass from the central equilibrium. |
| Simple Harmonic motion | Is a motion where acceleration is proportional to the displacement from the central equilibrium position and the direction of acceleration is always directed towards the central equilibrium position. |
a=-Ω2x Where Ω=angular velocity (s-1) x=displacement (m) The negative sign indicates that acceleration and displacement are in opposite direction. |
| Kinetic energy SHM |
Ek=½ mv2 v=+/-Ω sqrt(x02 – x2) Therefore: Ek=½ mΩ2(x02 – x2) Where m=mass(kg) Ω= angular velocity (s-1) x0= initial displacement from equilibrium (m) x= displacement from equilibrium (m) |
|
| Potential energy SHM | In a simple harmonic motion, there is a continual interchange between potential energy and kinetic energy (conservation of energy of an oscillating body- with no losses the total kinetic and potential energies is constant) |
Ep=Total Energy-Ek Ep=½ m Ω2x2
|
| Damping | Amplitude of the oscillating system decreases with time due to resistive forces opposing the motion. | |
| Light Damping | When the resistive force is small e.g air resistance, the amplitude of the oscillating system decreases very slowly with time. The frequency of the oscillating will be almost the same as the frequency of free oscillation. I.e period is remain the same throughout. | |
| Free oscillation | There are no external (resistive) forces; total energy remains constant, so amplitude constant. | |
| Critical damping | No oscillations and the system return to equilibrium in the shortest possible time. | |
| Heavy damping | No oscillations and the system return to equilibrium very slowly (after a period of time). | |
| Resonance | Resonance describes the phenomenon of increased amplitude that occurs when the frequency of a periodically applied force is equal or close to a natural frequency of the system on which it acts. | |
| Transducer | Is a device that converts one form of energy to another. | |
| Attenuation | The loss of power/ energy/ amplitude of signal. |
I0 = IR + IT Where: I0= Intensity of incident wave IR= Intensity of reflected wave IT= Intensity of transmitted wave. |
| Acoustic impedance | The product of the density of the medium and the speed of ultrasound wave in the medium. |
Z=ρc Where Z= Acoustic impedance ρ= Density of the medium c= Speed of ultrasound wave in the medium For wave incident normally at the boundary, the ratio of reflected to incident intensity given by: IR = (Z2-Z1)2/(Z2+Z1)2 = a Where: a= intensity reflection coefficient |
| Linear attenuation coefficient | Is the decrease in intensity of a parallel beam per unit length in the medium. Once the ultrasound is within the medium, the intensity of the wave will be reduced by absorption of energy as it is transmitted through the medium. The medium is heated. For a parallel beam, the absorption is approximately exponential. |
I=I0exp(-µx) Where: I= Transmitted (or) emergent intensity I0= Initial (or) incident intensity X= thickness of medium µ=(linear) absorption coefficient (or) attenuation coefficient µ=ln2/x½ |
| 13) Gravitational Force | ||
| Gravitational Field | Gravitational field is a region of space where in a mass will experience a force. | |
| Gravitational Field Strength | Gravitational Field Strength at a point is the gravitational force acting per unit mass at that point in the gravitational field. (force per unit mass) | g=GM/r2 |
| Newton’s law of gravitation | States that force is directly proportional to the product of the 2-point masses and inversely proportional to the square of the distance between them. |
FαMm and Fα1/r2 i.e FαMm/r2 Therefore: F=-GMm/r2 Where: F= Gravitational force of attraction (N) M,m= point masses (kg) r= distance between the two centres (m) G= universal gravitational constant (6.67×10-11Nm2kg-2) -ve sign is often omitted due to the attractive nature of gravitational force. |
| Gravitational potential energy |
Work done in bringing a mass from infinity to a point in the field. Gravitational potential and gravitational potential energy are zero at infinity. As gravitational force is attractive, work is done by the mass in moving from infinity to that point. |
Ep=-GMm/r
|
| Gravitational potential | Work done in bringing a unit mass from infinity to a point in the gravitational field. | Gravitational potential= -GM/r |
| Kepler’s 3rd Law | States that for a planet orbiting round the sun, the square of its period of revolution (T2)is proportional to the cubes of their mean distances from the Sun (r3) |
T2=(4π2/GM)R3 Where: M= mass of Sun R= radius about the Sun G= Universal gravitational constant T= Period of orbit |
| Geostationary | Refers to a circular orbit around the Earth where an orbiting satellite would appear stationary to an observer on the earth’s surface. | |
| Geostationary orbit for Earth | Orbits directly above Earth’s equator, moving from West to East with a period of 24hours. | |
| Escape Velocity | It is the minimum speed of an object needed to escape from the surface of a massive body (e.g a planet) and never return (i.e. completely escape Earth’s gravitational field). |
Ek at the surface = Gain in Ep in going to infinity ½ mv2=-GMm(1/rfinal – 1/rinitial) V=sqrt(2GM/R) |
| 14) Electric Force | ||
| Electric Field | An electric field is a region of space where an electric charge experiences a force. | |
| Electric Field Strength | Is the force acting per unit positive (stationary) charge. | |
| Coulomb’s Law | States that the force between 2 point charges is directly proportional to the product of the 2 point charges, and inversely proportional to the square of the distance between them. |
F α Qq/r2 FE= (1/4πΣ0).(Qq/r2) Where: (1/4πΣ0)=8.99×109 Q,q= 2 point charged particles (C) r= distance between the charges (m) Σ0= permittivity of free space i.e. in vacuum/aie |
| Electric potential energy | Electric potential energy at a point in free space is defined as the work done in bringing a positive charge (+q) from infinity to the point. | Ep= (1/4πΣ0).(Qq/r) |
| Electric potential | Electric potential at a particular point is the work done in bringing unit positive charge from infinity to that point. |
V=workdone/charge V= (1/4πΣ0).(Q/r) Zero potential is defined to be at infinity |