Viva - Physics Definitions Flashcards
Mass
Mass is a measure of an object’s inertia (i.e. its resistance to acceleration) and the kilogram is the SI unit.
Kilogram
A kilogram was originally intended to be the mass of 1000 cubic cm of water. Until recently it was referenced to a cylinder of platinum-iridium alloy kept in a laboratory in France. More recently it has been defined with reference to the Planck constant, but is still very close to the mass of 1L of water.
Mole
Mole is a measure of amount of substance, which is a measure of the elementary entities of a substance exist within an object or sample. One mole is equal to Avogadro’s number, 6.022*10^23 particles, which historically was defines as the same number of particles as exists in 12g of carbon-12.
Newton
The Newton is the SI unit of force, and equals the force required to give a 1kg object an acceleration of 1m/s^2.
Force
Force is an influence that causes the motion of an object with mass to change its velocity (i.e. to accelerate or decelerate). Force (N) = mass (kg) * acceleration (m/s^2)
Momentum
Momentum is the tendency of an object to remain in motion, and is measured as mass (kg) * velocity (m/s)
Kinetic energy
Kinetic energy is the energy an object possesses as a result of its motion.
KE = 1/2 * mass * velocity^2
It is the energy required to accelerate an object of a given mass from rest to its stated velocity.
Potential energy
Potential energy is the energy an object has because of either its position relative to another object (gravitational potential energy), stresses within itself (elastic potential energy), its electrical charge (electrical potential energy), etc.
Gravitational potential energy
GPE = height * mass * gravity
Pressure
Pressure is the force exerted perpendicular to the surface of an object per unit area. The SI unit is the Pascal (Pa)
Pressure = N / m^2 = kg / M.s^2
Pascal
The Pascal is the SI unit of pressure.
Pa = N / m^2 = kg / m.s^2
mmHg
A non-SI unit of pressure.
1kPa = 7.5mmHg
1kPa = 10.2cmH2O
Hydrogen Ion
A hydrogen ion, denoted H+, is a proton which has positive charge. The concentration of H+ ions in a solution is measured on the pH scale
pH
pH is the ‘power of hydrogen’.
pH = - log(10) [H+]
Being a negative logarithmic scale, each fall in pH by 1 means the concentration of H+ ions increases by a factor of 10
Critical temperature
The critical temperature is the temperature above which a particular gas can no longer be liquefied no matter how much pressure is applied to it.
Critical pressure
The critical pressure is the pressure required to liquefy a gas at its critical temperature. A substance at its critical temperature and pressure is at its critical point.
Triple point
The triple point of a substance is the temperature and pressure at which it can exist in equilibrium between solid, liquid and vapour phases.
Filling ratio
The filling ratio is the weight of the fluid in a cylinder, divided by the weight of water required to fill the cylinder.
Coulomb
The coulomb is the SI unit of electric charge. It is the amount of electricity that 1 Ampere current carries in one second. A quantity of 1 coulomb is equal to the electrical charge of 6.24*10^18 electrons or protons.
Ampere
The ampere is the SI unit of electrical current. Historically it was defined as the current that would need to be passed through 2 parallel wires of infinite length, 1 metre apart, in a vacuum, to produce a magnetic force of 210^-7 N / m. It is now defined as the electrical current when 6.2410^18 elementary charges move in one second.
Volt
The volt is the SI unit of electrical potential or electromotive force. It is defined as the electrical potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points, or equivalently the potential difference between two points that will impart one joule of energy per coulomb of charge that passes through it.
Volt = potential energy (J) / charge (C)
= kg.m^2 / A.s^3
It can also be expressed as V = I.R (amps*ohms)
Watt
The watt is the SI unit of power, which is energy per unit time (J/s)
Ohm
The ohm is the SI unit of resistance. It is the resistance of a conductor through which one amp of current flows when one volt is applied to it.
Hertz
Hertz is a measure of frequency in cycles per second.
Absolute humidity
The mass of water vapour present in a given volume of air at a given temperature - kg.m^-3
Relative humidity
The mass of water in a given volume of air, expressed as a percentage of the maximum mass of wter that the air could hold at the given temperature.
Absolute zero
The lowest possible temperature, where all thermal motion of particles ceases - 0K or -273.15’C
Boiling point
The temperature at which the vapour pressure of a liquid equals the surrounding ambient pressure and liquid changes into a vapour.
Calorie
The amount of energy required to increase the temperature of 1g (1cm^3) of water by 1’C. 1 calorie = 4.16 J
Freezing point
The temperature at which the liquid and solid phases of a substance of specified composition are in equilibrium at a given pressure. A liquid turns into a solid when its temperature is lowered below its freezing point.
Gas
One of the four fundamental states of matter found between the liquid and plasma phase (four states = solid, liquid, gas, and plasma). There is vast separation between individual molecules and the gas will expand to fill any space available.
Heat capacity
The amount of heat required to raise the temperature of an object by 1’C (specific heat capacity x mass of body). SI unit is J.K^-1
