public void makeCannonBall() {
    /* Create a cannonball geometry and attach to scene graph. */
    Geometry ball_geo = new Geometry("cannon ball", sphere);
    ball_geo.setMaterial(stone_mat);
    rootNode.attachChild(ball_geo);
    /* Position the cannonball.  */
    ball_geo.setLocalTranslation(cam.getLocation());
    /* Make the ball physical with a mass > 0.0f */
    RigidBodyControl ball_phy = new RigidBodyControl(1f);
    /* Add physical ball to physics space. */
    ball_geo.addControl(ball_phy);
    bulletAppState.getPhysicsSpace().add(ball_phy);
    /* Accelerate the physical ball to shoot it. */
    ball_phy.setLinearVelocity(cam.getDirection().mult(25));
  }
Creates one physical cannonball.
By default, the ball is accelerated and flies
from the camera position in the camera direction.
jme3-examples/src/main/java/jme3test/helloworld/HelloPhysics.java