BGCSE Physics 1427 flashcards
BGCSE Physics 1427 · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Newton's second law
- The resultant force on a body equals its mass times acceleration (F = ma); one newton accelerates one kilogram at one metre per second squared.
- Moment of a force
- The turning effect of a force, calculated as force multiplied by the perpendicular distance from the pivot to the line of action, measured in newton metres.
- Principle of moments
- For a body in rotational equilibrium, the sum of clockwise moments about any point equals the sum of anticlockwise moments about that same point.
- Kinetic energy
- Energy a body possesses due to its motion, given by one half times mass times velocity squared; doubling the speed quadruples the kinetic energy.
- Conservation of momentum
- In a closed system with no external resultant force, total momentum before a collision equals total momentum after; momentum is mass times velocity.
- Efficiency of a machine
- Useful output energy, or power, divided by total input energy, or power, expressed as a percentage; no machine reaches 100% because friction dissipates energy.
- Ohm's law
- Provided temperature stays constant, the current through a metallic conductor is directly proportional to the potential difference across it.
- Resistance
- Potential difference across a component divided by the current through it, measured in ohms; one ohm carries one ampere with one volt applied.
- Series circuit
- A single-path circuit in which the current is the same at every point, the supply voltage is shared between components and the resistances add together.
- Parallel circuit
- A circuit with branches where the potential difference across each branch is the same and the total current equals the sum of the branch currents.
- Electromagnetic induction
- An emf is induced in a conductor whenever the magnetic flux linking it changes, such as when a magnet is moved into a coil.
- Lenz's law
- The direction of an induced current always opposes the change producing it, which is a consequence of the conservation of energy.
- Wave equation
- Wave speed equals frequency multiplied by wavelength; for sound in air the speed is about 340 metres per second at room temperature.
- Refraction
- The change in direction of a wave when it crosses a boundary between media of different densities, caused by a change in wave speed.
- Snell's law
- For light crossing a boundary, the refractive index n equals the sine of the angle of incidence divided by the sine of the angle of refraction.
- Critical angle
- The angle of incidence in the denser medium above which total internal reflection occurs; its sine equals one divided by the refractive index.
- Convex lens
- A converging lens that brings parallel rays to a principal focus; it forms a real inverted image unless the object is closer than the focal length.
- Diffraction
- The spreading of waves when they pass through a gap or around an obstacle; it is greatest when the gap is similar to the wavelength.
- Specific heat capacity
- The energy needed to raise the temperature of one kilogram of a substance by one degree Celsius, measured in joules per kilogram per degree Celsius.
- Specific latent heat
- The energy needed to change the state of one kilogram of a substance without changing its temperature, for example during melting or boiling.
- Conduction
- Transfer of thermal energy through a material by vibrating particles and free electrons, without any bulk movement of the material itself.
- Convection
- Transfer of thermal energy by the bulk movement of a fluid, in which warmer, less dense regions rise and cooler regions sink.
- Thermal radiation
- Infrared electromagnetic waves emitted by all bodies above absolute zero; dark matt surfaces are the best absorbers and the best emitters.
- Isotopes
- Atoms of the same element with identical proton numbers but different nucleon numbers, because they have differing numbers of neutrons in the nucleus.
- Alpha particle
- A helium nucleus of two protons and two neutrons emitted in radioactive decay; it is strongly ionising but is stopped by paper.
- Half-life
- The time taken for half the unstable nuclei in a sample to decay, or for the activity of the sample to fall to half.
- Beta decay
- Radioactive decay in which a neutron in the nucleus turns into a proton, emitting a fast electron; the proton number rises by one.
- Gamma radiation
- High-energy electromagnetic radiation emitted from an excited nucleus; it has no charge or mass and is stopped only by thick lead.
- Random error
- An unpredictable variation in readings that scatters results above and below the true value; it is reduced by repeating measurements and averaging.
- Systematic error
- A consistent offset affecting every reading by the same amount, such as a zero error, which shifts the mean away from the true value.
- Vernier calliper
- An instrument measuring internal, external and depth dimensions, read from the main scale plus the vernier scale, typically to 0.1 millimetre.
- Precision and accuracy
- Precision is how closely repeated measurements agree with each other, while accuracy is how close a measurement lies to the true value.