Category : Science and Education
Archive   : GRAVITY2.ZIP
Filename : GRAVITY.HLP

 
Output of file : GRAVITY.HLP contained in archive : GRAVITY2.ZIP


MAIN MENU
Move the highlight with the arrow keys
then make a selection with the ENTER key.


MASS
Enter the mass of the planet
in Kilograms (Kg). The number
given must be greater than or
equal to zero.


DENSITY
Enter the density of the planet in
Kilograms per cubic Meter (Kg/M^3).
The value given must be greater than
zero. The density of water is 1000
(1E03) Kg/M^3.


X POSITION
Enter the X position of the
planet in Meters.


Y POSITION
Enter the Y position of the
planet in Meters.


X VELOCITY
Enter the X component of the
velocity in Meters per Second (M/s).


Y VELOCITY
Enter the Y component of the
velocity in Meters per Second (M/s).


ORBITS
This field enables plotting of the
orbit dots that mark the path of
the planet as it moves. The dots
will only display if the Show Orbits
setting under the Misc menu is ON.
Valid values for this field are Y
and N.


STATIONARY
This locks the planet firmly in
place. New position values are
not calculated for stationary
planets. This is an imaginary
condition and should not be used
if you are modeling an actual
system.


ZOOM POWER
Changing the zoom power allows you to
"Zoom-in" and "Zoom-out" to view orbit-
ing bodies at varying magnifications.
To zoom-out and see the whole system,
use small values. To zoom-in and make
objects appear very big, use larger
values.

This value is also changeable from
the running simulation by using the
PgUp, PgDn, and Home keys.


X CENTER
This is effectively a panning value. You
enter where in space you would like the
center of the screen (X direction) to show.

This value is also changeable from the
running simulation by using the arrow
keys in conjunction with PgUp and PgDn.


Y CENTER
This is effectively a panning value. You
enter where in space you would like the
center of the screen (Y direction) to show.

This value is also changeable from the
running simulation by using the arrow
keys in conjunction with PgUp and PgDn.


TIME INTERVAL
Time Interval is how long a force acts on a
planet in seconds, or in other words, the
elapsed time between new velocity and position
calculations. The planet motions are simulated
not by curves, but by many very short lines.
The time interval relates to the length of those
lines. Since in reality they are 0 in length,
the smaller this number the better. You may
lower this number for accuracy, or increase it
for speed. If the planets are not moving more
than a few pixels per plot, depending on how
sharply curved the planet path is, the accuracy
you are getting is probably fine. This value
can be automatically determined with the Dynamic
Time Interval function ('D' on the simulation
screen).


GRAVITATIONAL CONSTANT
The gravitational constant is the strength
of the gravitational field. You should not
need to change this value, but it is included
for versatility. Changing it will affect the
units used for mass, density, distance, and
velocity. The value of +6.67E-11 is the
actual value found in reality.


CALCULATIONS PER PLOT
Actually a bit of a misnomer, this really
relates to Plots per Calculation. It only
affects the frequency of plotting positions
on the screen, not how the calculations
are done, or the paths planets will take.
You may want to change this when you are
watching the Status Line, or if you have
very slow display hardware.


CENTRAL PLANET TRACKING
You can watch the simulation from the perspective
of any one of the defined planets. This will plot
the specified planet in the center of the screen
and the other planets will move in relation to it.
This does not affect how the calculations for move-
ment are performed, only how the planets are disp-
layed. Using this, you can follow the orbit of one
system which is part of a larger system. For
instance, you can watch the earth-moon system up
close while it revolves around the sun without
having to do zoom/pan/zoom/pan/etc. An entry
of 0 will turn off this feature.

This function is also available from the running
simulation by pressing first the 'C' key, and then
the key for the planet you want to track
(1-9, ! @ # $ % ^ &).


STATUS LINE
Displays the current status of a planet. Values
displayed include: Planet number, Mass, Position,
and Velocity. If the planet collides with another,
the status switches to the live planet. A value
of 0 turns this function off.

This function is also available from the running
simulation by pressing first the 'S' key, and then
the key for the planet you want the status displayed
for (1-9, ! @ # $ % ^ &).


SAVE FILE
Enter the full drive, path, and name of the
file you want to save to. If you omit the
path, the current directory is assumed.
If you omit the extension, .GRV is appended.


RESTORE FILE
Enter the full drive, path, and name of the
file you want to read from. If you omit
the path, the current directory is assumed.
If you omit the extension, .GRV is appended.


Answer with the Y or N key.