Android: Using Accelerometer to Calculate Total Force

I'm in the process of building an app that calculates how far you could throw something, based on the speed you swing your phone. This involves tracking your phone's movement as you swing it, and calculating the total maximum force involved. I couldn't find any examples on how to do this, so I've mocked up a bit of a tutorial below.

How do we get the accelerometer values?

private SensorManager mgr=null;
mgr=(SensorManager)ctxt.getSystemService(Context.SENSOR_SERVICE);
mgr.registerListener(listener,
mgr.getDefaultSensor(Sensor.TYPE_ACCELEROMETER),
SensorManager.SENSOR_DELAY_UI);


private SensorEventListener listener=new SensorEventListener() {
        public void onSensorChanged(SensorEvent e) {
            if (e.sensor.getType()==Sensor.TYPE_ACCELEROMETER) {
                //Total acceleration will be sqrt(x^2+y^2+z^2)
                double netForce=e.values[0]*e.values[0];    //X axis               
                netForce+=e.values[1]*e.values[1];    //Y axis
                netForce+=(e.values[2])*(e.values[2]);    //Z axis (upwards)
               
                netForce = Math.sqrt(netForce) - SensorManager.GRAVITY_EARTH;    //Take the square root, minus gravity
               
                Log.d("ForceCalculator", "Net force:"+netForce+"");
            }
        }
       
        public void onAccuracyChanged(Sensor sensor, int accuracy) {
            // unused
        }
    };


This will create and register an event listener for the accelerometer. This listener then calculates the net force.

This calculation is pretty self-explanatory. It involves three components - X axis, Y axis, and Z axis. To calculate the magnitude of these vector components, we simply take the square root of their combined squares:
netForce = sqrt( x^2 + y^2 + z^2 )
The only point to note is that we then subtract the acceleration due to gravity (approx. 9.8m/s^2). Otherwise we could have a resting acceleration of +9.8.

Full code will be coming later, when I've got some more time to play around with it. For now, this should show you how to get net force using the accelerometer. Still to come is code to calculate maximum force over a specified period of time, with threshold starting and finishing velocities.