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