Creating Physics World:

• Make sure you have Physics Extension linked to your project.

Here`s example how to create new physics world:

private PhysicsWorld physicsWorld;

private void initPhysics()
{
    physicsWorld = new PhysicsWorld(new Vector2(0, SensorManager.GRAVITY_EARTH), false);
    yourScene.registerUpdateHandler(physicsWorld);
}

1. How to control gravity?

While creating new physics world, we have to specify new Vector2, with two parameters, responsible for gravity forces, first one for the x-component, second one for the y-component. In most cases, we will use 0 in first one. But you might specify there your own value, if you want to stimulate y-component force, for example similar to the WIND.

2. Using FixedStepPhysicsWorld:

Creating FixedStepPhysicsWorld is mostly the same, with obviously main difference, we are using different class (subclass of the standard PhysicsWorld) this implementation has one more additional parameter, as mentioned about responsible for FPS count, that subclass tries to achieve a specific amount of steps per second. There isn't any fixed value you should use, everything depends on your needs, be aware that sometimes you may need different value, to achieve smooth physics. But in another hand to big value might be bad for cheaper devices, that's why be considerate.