June 2018 Update

Task/Animate-a-pendulum/BASIC/animate-a-pendulum-1.basic

@@ -0,0 +1,29 @@
+      MODE 8
+      *FLOAT 64
+      VDU 23,23,4;0;0;0; : REM Set line thickness
+
+      theta = RAD(40) : REM initial displacement
+      g = 9.81 : REM acceleration due to gravity
+      l = 0.50 : REM length of pendulum in metres
+
+      REPEAT
+        PROCpendulum(theta, l)
+        WAIT 1
+        PROCpendulum(theta, l)
+        accel = - g * SIN(theta) / l / 100
+        speed += accel / 100
+        theta += speed
+      UNTIL FALSE
+      END
+
+      DEF PROCpendulum(a, l)
+      LOCAL pivotX, pivotY, bobX, bobY
+      pivotX = 640
+      pivotY = 800
+      bobX = pivotX + l * 1000 * SIN(a)
+      bobY = pivotY - l * 1000 * COS(a)
+      GCOL 3,6
+      LINE pivotX, pivotY, bobX, bobY
+      GCOL 3,11
+      CIRCLE FILL bobX + 24 * SIN(a), bobY - 24 * COS(a), 24
+      ENDPROC

Task/Animate-a-pendulum/BASIC/animate-a-pendulum-2.basic

@@ -0,0 +1,24 @@
+10 GOSUB 1000
+20 THETA = π/2
+30 G = 9.81
+40 L = 0.5
+50 SPEED = 0
+60 PX = 20
+70 PY = 1
+80 BX = PX+L*20*SIN(THETA)
+90 BY = PY-L*20*COS(THETA)
+100 PRINT CHR$(147);
+110 FOR X=PX TO BX STEP (BX-PX)/10
+120 Y=PY+(X-PX)*(BY-PY)/(BX-PX)
+130 PRINT CHR$(19);LEFT$(X$,X);LEFT$(Y$,Y);"."
+140 NEXT
+150 PRINT CHR$(19);LEFT$(X$,BX);LEFT$(Y$,BY);CHR$(113)
+160 ACCEL=G*SIN(THETA)/L/50
+170 SPEED=SPEED+ACCEL/10
+180 THETA=THETA+SPEED
+190 GOTO 80
+980 REM ** SETUP STRINGS TO BE USED **
+990 REM ** FOR CURSOR POSITIONING   **
+1000 FOR I=0 TO 39: X$ = X$+CHR$(29): NEXT
+1010 FOR I=0 TO 24: Y$ = Y$+CHR$(17): NEXT
+1020 RETURN

Task/Animate-a-pendulum/BASIC/animate-a-pendulum-3.basic

@@ -0,0 +1,22 @@
+Const PI = 3.141592920
+Dim As Double theta, g, l, accel, speed, px, py, bx, by
+theta = PI/2
+g = 9.81
+l = 1
+speed = 0
+px = 320
+py = 10
+Screen 17 '640x400 graphic
+Do
+    bx=px+l*300*Sin(theta)
+    by=py-l*300*Cos(theta)
+    Cls
+    Line (px,py)-(bx,by)
+    Circle (bx,by),5,,,,,F
+    accel=g*Sin(theta)/l/100
+    speed=speed+accel/100
+    theta=theta+speed
+    Draw String (0,370), "Pendulum"
+    Draw String (0,385), "Press any key to quit"
+    Sleep 10
+Loop Until Inkey()<>""