Ro

Road Noise
Generated by the interaction of the tyre with the road.
Roche Limit
The position around a massive body where the tidal forces due to the gravity of the primary equal or exceed the surface gravity of a given satellite.
Rock Tunnel
A passage constructed through solid rock.
Rocker Arm
A lever that transmits the action of the cam, usually by means of a push rod, to the stem of the intake or exhaust valve, sometimes also to the starting-air valve and fuel valve.
Rocket
Commonly used term for a launch vehicle.
Rocket Assisted Takeoff
Utilising solid or liquid fuel rockets to augment the take-off.
Rocket Engine
A reaction engine that carries all fuel and components for combustion and so not requiring intake of any outside substance and hence capable of operation in outer space.
Rocket Fuel
A fuel, either liquid or solid, developed for, or used by, a rocket.
Rocket Nozzle
The exhaust nozzle of a rocket engine.
Rocket Propellant
Any agent used for consumption or combustion in a rocket and from which the rocket derives its thrust, such as a fuel, oxidizer, additive, catalyst, or any compound or mixture of these.
Rocket Sled
A sled that runs on a rail or rails and is accelerated to high velocities by a rocket engine.
Rocket Sounding
A probe of the upper atmosphere with a meteorological rocket to produce a record of the vertical variation of a weather element such as air temperature, density, composition or winds.
Rocketsonde
An instrument package carried aloft by a meteorological rocket to make a measure one or more weather elements in a sounding of the upper atmosphere.
Rocking Grate
An advanced form of firebar.
Rockoon
A high-altitude sounding system consisting of a small solid-propellant research rocket carried aloft and launched by a large balloon.
Rockwell Hardness
Hardness determined from size of indentation using a diamond or steel ball and given load.
Rococo
A style originating in France around 1720 and developed out of Baroque, characterized by its ornamentation of shellwork and foliage.
Rod
An old English unit of length.
Roentgen
The roentgen is a unit used to measure radiation exposure.
Roentgen Equivalent Man (rem)
This relates to the absorbed dose in human tissue to the effective biological damage of the radiation.
Roll
The oscillation of a rigid body which consists primarily of angular displacement about a central longitudinal axis with respect to its static position.
Roll Axis
Longitudinal line around which a vehicle rolls (joins front and rear roll centres).
Roll Bar
Abbreviated name for Anti-Roll Bar.
Roll Centre
Invisible moving point around which a vehicle is considered to rotate in a corner.
Roll Cloud
A relatively rare, low-level, horizontal, tube-shaped cloud.
Roll Off
A measure of the attenuation of a filter with frequency.
Rolled Thread
A thread formed by plastically deforming a blank rather than by cutting.
Roller Bearing
A bearing in which the relatively moving parts are separated by rollers.
Roller Joint
Allows adjacent parts to move controllably past one another.
Roller Support
In two dimensions, a roller support restrains one translation degree of freedom.
Roller Tappets
Valve lifters that have a roller placed on the end contacting the camshaft. This is done to reduce friction between the lobe and lifter.
Rolling Drag
Another name for Rolling Resistance.
Rolling Friction
Another name for Rolling Resistance.
Rolling Resistance
The resistance that occurs when a round object such as a ball or tire rolls on a flat surface.
ROM
Read only memory (permanent memory that cannot be changed).
Roman Numerals
The roman number system with decimal equivalents.
Romanesque
Style developed in western and southern Europe after 1000 and characterized by heavy masonry, the round arch, barrel and groin vaults, narrow openings, vaulting rib, the vaulting shaft, and central and western towers.
RON
Abbreviation for Research Octane Number.
Roof
The covering on the uppermost part of a building.
Room
An enclosed space.
Room Absorption
Sum of Sabine absorption due to objects and surfaces in a room, and due to dissipation of energy in the medium within the room.
Room Acoustics
The general acoustic requirements of a room depend on the use.
Room Constant
The ratio of room sound absorption to the quantity 1 minus the average room absorption coefficient.
Room Modes
Frequencies at which sound waves in a room resonate (in the form of standing waves), based on the room dimensions.
Root
A root of a polynomial function, f, is just a solution to the equation f(x) = 0, that is an input that yields an output of 0.
Root Mean Square
This is the square root of sum of squares of individual observations divided by the total number of observations made.
Root of Unity
A solution of the equation xn=1, where n is a positive integer.
Rosenbrock Function
A non-convex function used as a performance test problem for optimization algorithms introduced by Rosenbrock in 1960.
Roses Alloy
A fusible alloy consisting of 50 per cent bismuth, 25 percent lead and 25 per cent tin.

Rosin
Natural resin obtained from living pine trees or from dead tree stumps and knots.

Rotary Engine
The crankshaft is fixed and the crankcase, pistons and cylinders rotate with the propeller.
Rotary Inverter
A device having a combination motor generator with a governor which inverts DC to AC.
Rotary Pump
A pump that moves fluid by positive displacement, using a system of rotating vanes, gears, or lobes.
Rotary Switch
A multicontact switch with contacts arranged in a circular or semicircular manner.
Rotate
To rotate an object in a tessellation means to repeat the object by spinning it on a point a certain angle.
Rotating Field
The magnetic field in a multiphase ac motor that is the result of field windings being energized by out-of-phase currents.
Rotating Seal
When the spring loaded or moveable portion of the seal rotates with the shaft.
Rotation
Motion of an object where the path of every point is a circle or circular arc.
Rotational Inertia
The property of an object that measures its resistance to a change in its rotational speed.
Rotational Kinetic Energy
The energy a body possesses due to it's rotation about an axis.
Rotational Play
Looseness, usually in a coupling, where a rotor can rotate a given distance before the rotational play is out and the coupled shaft begins to rotate also.
Rotor
A rotating part.
Rotor Cloud
An altocumulus cloud formation that can be found in the lee of a mountain or similar barrier.
Rough Machining
Removing excess material with a machine tool thus shaping it in preparation for finish machining.
Roughing
The fast removal of stock to reduce a workpiece to approximate dimensions. leaving only enough material to finish the part to specifications.
Roughing Stone
A coarse stone used for quick removal of material during honing.
Round File
A file in the shape of a round bar.
Round Nose Chisel
Used for cutting semi-circular grooves for oil ways in bearings.
Round Nose Pliers
Pliers with a round nose.
Round Off
To delete less significant digits from a number and possible apply some rule of correction to the part retained.
Round Off Error
This is error introduced into a calculation by rounding off the results of intermediate steps to values which are close, but not exactly correct.
Round Window
The tiny membrane of the cochlea that opens in the middle ear that serves as a "pressure release" for the cochlear fluid.
Rounding
A numerical value means replacing it by another value that is approximately equal but has a shorter, simpler, or more explicit representation.
Round-Off Error
The error accumulated during a calculation due to rounding intermediate results.
Router
Basically a high speed motor with handles and an adjustable base with a collet that accepts profile bits to cut dados, rabbets, or shapes.
Router
A device that routes information between interconnected networks.
Routing Information Protocol
A protocol, limited to a small number of machines attached to LANs, used to exchange Internet routing information across networks.
Roving
A collection of bundles of continuous filaments either as untwisted strands or as twisted yarns.
Row Equivalent Matrices
Two matrices are row equivalent if one can be obtained from the other by a sequence of elementary row operations.
Row Space of a Matrix
The subspace spanned by the rows of the matrix considered as a set of vectors.