1000 REM SATEL
SCREEN 12:CLS
 G=6.67E-11:REM GRAVITY CONSTANT
 MZ=5.975E24:REM MASS OF THE EATH
 RZ=6378000
 MS=1000:REM SATELITE MASS
 DT=.3:REM TIME QUANT
 XC=320:YC=240:KY=(800/(3*640))*(480/200)
 'INPUT"INPUT WATCHIN' VESINITY (KM.)(RECOMENDED-10000)";RM
 RM=10000
 Q=(200/(1000*RM))
 'INPUT"INITIAL HIGH (KM)";H
 H=300
 H$="INITIAL HIGH="
 H=H*1000
 R1=Q*RZ
 'INPUT"SATELITE VELOSITY (KM/SEC)";V
 V$="INITIAL VELOSITY="
 V=8
 VX=V*1000:VY=0
 X=0:Y=RZ+H
 CLS
 ?H$;H/1000;"KM":?V$;V;"KM/SEC"
 ?
 ?"HIT <ESC> - TO QUIT"
 OX=X:OY=Y
 CIRCLE(XC,YC),R1:PAINT(XC,YC),9
 CIRCLE(XC,YC),R1,0
KRUTIM:
  CIRCLE(XC+OX*Q,YC+KY*Q*OY),1.5,0
  CIRCLE(XC+X*Q,YC+KY*Q*Y),1.5,11
  R=SQR(X*X+Y*Y)
  F=G*MZ*MS/(R*R)
  FX=-F*X/R:FY=-F*Y/R
  AX=FX/MS:AY=FY/MS
  DVX=AX*DT:DVY=AY*DT
  VX=VX+DVX:VY=VY+DVY
  OX=X:OY=Y
  X=X+VX*DT:Y=Y+VY*DT
  IF INKEY$=CHR$(27) THEN STOP
  GOTO KRUTIM