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Gravity
GlossaryA
Rate of change of velocity (a vector quantity) = change of velocity/time taken.
Force in operation.
Force opposing motion through the air.
Not moving against the local frame of reference (background).
Total distance covered divided by total time taken (regardless of speed changes during the motion).
B
C
Laboratory apparatus using the attraction between lead and brass spheres to twist a sensitive fibre and so measure the gravitational force.
The necessary force acting radially in towards the centre of a circle to keep an object moving in that circular path.
The total distance around the edge of a circle.
The period of mistrust, suspicion and ideolgical rivalry between the USA and the USSR lasting from the end of World War II till the break up of the USSR.
A value that does not change.
D
E
A moving object has energy simply because it is moving and work must be done (energy expended) to stop it.
An object given this vertical velocity at the Earth's surface has sufficient energy of motion to escape the Earth's gravitational field completely.
F
Motion through the air generating sufficient lift force to counteract the weight of the flying object - used also to refer to motion through space.
Different methods of flight - referring to speeds, propulsion systems and trajectories.
Basically a 'push' or a 'pull' - usually causing a change of motion.
G
Einstein's spectacular theory equating gravity to the curvature of space-time and explaining the bending of light beams.
Able to produce some lift force as it falls through the air - enabling the vehicle to manouver.
Force of attraction (a pull) between any two masses by virtue of their mass alone - attributed to gravity.
Universally unchanging multiplying factor for product of two massses divided by the square of their separation that converts to actual attractive force value.
Energy by virtue of distance of one mass from another attracting mass (potential energy).
Region of space in which masses feel gravitational attracting forces also defined as 'force per kilogram' at the point in question.
Attracting force between any two masses.
Attracting force caused by gravity - usually in the region of a star or planet.
The agency that brings about the attraction between all masses in the Universe.
H
J
K
L
Energy can never be created or destroyed but only converted from one form to others.
Newton's theory that states that any two masses attract each other with a force proportional to the product of their masses divided by their separation squared.
Newton's three laws relating forces and the motion of masses on which they act.
M
Affects how easily an object can change motion - represents the 'amount of matter' present in the object - gives rise to graviational attraction.
Any nuclear atttack would unavoidably produce a full exchange of nuclear weapons virtually guaranteeing the total destruction of both nations involved.
O
Circular or elliptical path around a central object.
The necessary velocity for an object to maintain an orbit of that particular radius (altitude).
To move rhythmically back and forth about a central (rest) position - with changing velocity and acceleration.
P
By maintaining an orbit at a particular altitude an object can maintain velocity without using engine power. A 'synchronous' orbit has a period of 24hrs and so can be used to 'park' a satellite above a fixed point on the equator.
The time taken to make one complete orbit.
Q
R
The shortest distance from the centre of a circle to a point on the circumference.
Response to a force (action and reaction are equal and opposite).
Ideas that become relevant when speeds approach the speed of light - according to Einstein's Special Theory of Relativity.
A vehicle propelled by emitting gases at very high velocity - moving by reaction in the opposite direction to the gases.
S
An object in stable orbit round a central mass - man-made or natural.
As part of the cold war, both the USA and USSR wanted to make the first 'moves' in space exploration - hence there was an undeclared 'race'.
Distance moved divided by time taken.
Three dimensionally symmetric round objects of circular profile (balls).
T
Geographical regions in which war is taking or has taken place.
See 'law of gravitation' and 'law(s) of motion'.
Very small forces can be measured by arranging them to twist a sensitive fibre.
Twisting forces.
U
Newton's theory that states that any two masses attract each other with a force proportional to the product of their masses divided by their separation squared.
W
Work is done whenever a force moves along its line of action ie: newtons times metres equals Joules of work.
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