X-Git-Url: https://git.gag.com/?a=blobdiff_plain;ds=sidebyside;f=ao-tools%2Fao-fakeflight%2Fao-physics.c;fp=ao-tools%2Fao-fakeflight%2Fao-physics.c;h=114b9e0f927da6304cdc6d2cd8f414287f0702d1;hb=248aaf5e76292c8e6bfa3600d2cf9b194bf66c86;hp=0000000000000000000000000000000000000000;hpb=4f2cbe0c537c9f417aae310cc3b89f84e0915103;p=fw%2Faltos

diff --git a/ao-tools/ao-fakeflight/ao-physics.c b/ao-tools/ao-fakeflight/ao-physics.c
new file mode 100644
index 00000000..114b9e0f
--- /dev/null
+++ b/ao-tools/ao-fakeflight/ao-physics.c
@@ -0,0 +1,53 @@
+/*
+ * Copyright © 2014 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "ao-fakeflight.h"
+
+/* Density of dry air in kg/m³ for a given pressure and temperature. */
+double
+density_air(double pressure,		/* Pa */
+	    double temperature)		/* °C */
+{
+	return pressure / (GAS_CONSTANT * (temperature + 273.15));
+}
+
+/* Area of a circle */
+double
+area_circle(double diameter)
+{
+	double radius = diameter / 2;
+	return M_PI * radius * radius;
+}
+
+/* Force due to drag (N) */
+double
+force_drag(double	speed,		/* m/s */
+	   double	rho,		/* kg/m³ */
+	   double	cd,		/* unitless */
+	   double	area)		/* m² */
+{
+	return 0.5 * rho * (speed * speed) * cd * area;
+}
+
+/* Force due to gravity (N) */
+double
+force_gravity(double	mass,		/* kg */
+	      double   	altitude)	/* m */
+{
+	double	distance = altitude + EARTH_RADIUS;
+	return GRAVITATIONAL_CONSTANT * EARTH_MASS * mass / (distance * distance);
+}