V

vacuum - a region that is totally empty
vapour - a gas below the boiling point of the substance
variable - something that changes, usually in an experiment
variable resistor - a resistor whose value can be changed, used in volume controls
variable star - a star whose brightness changes in a regular way
vector - quantity with both size and direction (e.g. force, velocity, displacement)
VDU - visual display unit
velocity - speed in a particular direction
velocity ratio - in a machine, distance effort moves/distance load moves in the same time
Venus - second planet from the Sun
vernal equinox - spring equinox
vernier - device for measuring small distances to within 0.1 mm
VHF - very high frequency
vibration - oscillation, wobble, a regular movement backwards and forwards
vibration generator - apparatus for producing linear mechanical oscillation
virtual image - one formed in space, a point from which the rays appear to diverge
viscosity - resistance to motion of/in a fluid. Its 'stickiness'. Units Pas.
viscous drag - the drag force on an object moving through a fluid due to the viscosity of the fluid
visible - something that you can see
vitreous humour - fluid in the main body of the eyeball (between the lens and the retina)
volatile - liquids that vaporise easily
volt - the electrical energy per unit charge
voltameter - apparatus in which electrolysis is carried out
voltmeter - instrument for measuring voltage
volume - three dimensional space occupied by a body
vortex - a region where fluids spiral inwards, a whirling region
Voyager - space missions to the outer planets (launched 1977)