液体内部的压强是初中物理教与学的难点,在计算时,深度跟选取的参考面有关。深度是指液面向下到该处的竖直距离。也就是选取液面作为参考面,若该处在参考面下方时,压强大于参考面压强。若该处在参考面上方时,压强小于参考面压强。通常我们规定,在参考面下方时,深度取正值,在参考面上方时,深度取负值。如在托里拆利实验中(见图),若取玻璃管内水银面为参考面时,A点在参考面下方,深度为(h+h_A)。B点也在参考面 The pressure inside the liquid is a difficulty in physics teaching and learning in junior middle school. When calculating, the depth is related to the selected reference surface. Depth is the vertical distance that the liquid faces down to this point. That is, the liquid surface is selected as a reference surface. If the liquid surface is below the reference surface, the pressure is stronger than the reference surface pressure. If this is above the reference plane, the pressure is less than the reference surface pressure. Normally, we specify that the depth is a positive value below the reference plane and negative when it is above the reference plane. As in the Torricelli experiment (see figure), if the mercury surface inside the glass tube is used as the reference surface, point A is below the reference plane and the depth is (h+h_A). Point B is also on the reference plane