bd3.type = BodyType.DYNAMIC;
bd3.position.set(2.5f, 12.0f);
Body body3 = m_world.createBody(bd3);
body3.createFixture(box, 5.0f);
PrismaticJointDef jd3 = new PrismaticJointDef();
jd3.initialize(ground, body3, bd3.position, new Vec2(0.0f, 1.0f));
jd3.lowerTranslation = -5.0f;
jd3.upperTranslation = 5.0f;
jd3.enableLimit = true;
m_joint3 = (PrismaticJoint) m_world.createJoint(jd3);