Abstract
In this research, the possibility of using the rising and dropping time of vegetables through water as a means of hydro-sorting of tomato and potato was studied. The dropping time of potato and rising time of tomato were theoretically formulated and then determined experimentally using water column. The best models for dropping time of potato (cv. Analytic) and rising time of tomato (cv. Rio grand s) as a function of water and vegetable densities, shape factor and vegetable volume were modelled with determination coefficients of 0.95 and 0.91, respectively. It was found that difference between vegetables and water densities had major effect on rising and dropping time. It can be concluded that in the sorting systems, difference in terminal velocities of vegetables can be used as a suitable factor for design the sorting system devices.