Concrete is to be poured for a large foundation, but a round passageway is required through the concrete to carry utilities through it. A lightweight plastic tube will be placed horizontally in the empty form to keep this duct way open and then wet concrete (sg = 2.6) will be poured into the form and around the tube. Since this tube of negligible weight will be buoyed up while the concrete mix is wet, it must be tethered down to keep it from floating up though the wet concrete mix. If this tube is 120 cm in diameter, how much force, per meter of length, must be provided to tether it down and hold it in place until the concrete sets?