bd.position.set(0.0f, 17.0f);
Body body = getWorld().createBody(bd);
body.createFixture(shape, 2.0f);
RevoluteJointDef rjd = new RevoluteJointDef();
rjd.initialize(prevBody, body, new Vec2(0.0f, 17.0f));
getWorld().createJoint(rjd);
PrismaticJointDef pjd = new PrismaticJointDef();
pjd.initialize(ground, body, new Vec2(0.0f, 17.0f), new Vec2(0.0f, 1.0f));