A horizontal conveyor belt moving at 0 9m s receives sand from a hopper. The sand falls vertically from the hopper to the belt at a speed of 1 5m s and a flow rate of 225 kg s (the density of sand is approximately 1580 kg m3). The conveyor belt is initially empty but begins to fill with sand. If friction in the drive system and rollers is negligible, find the tension required to pull the belt while the conveyor is filling.