Because the stream moving along the bottom displaces the lighter fluid upward, a force must be provided to overcome boundary resistance . 因为沿底部运动的异重流与上部较轻的流体置换，必须产生一种力来克服边界阻力。
Because of local resistance, federal intervention may be necessary to designate certain sites for hazardous-waste-disposal facilities . 由于地方上的阻力，或许有必要通过联邦政府的调解来指定某些近便的有害废物处理场。
In the absence of air resistance, the only force on a projectile is its weight, and the mechanical energy of the projectile remains constant . 忽略空气阻力，作用在抛体上的力只是它的重量，因而该抛体的机械能是守恒的。
Youths, through inexperience of obstacles and of their own shortcomings, easily count a thing possible, and consequently are of good hope . 青年人由于对阻力和自己的缺点没有经验，很容易把事物看成是可能的，因此满怀好的希望。
Gilbert speculates that the reason for this increase of transport rate is the reduction of friction losses by the presence of fine suspended material in the flow . 吉尔勃特认为输沙率增加的理由，是水流中存在的细悬移泥沙将减少阻力损失。
These anemometers, which employ hot wires, sonics, drag spheres, etc, are not commonly used because of operational and other difficulties . 这些风速计是使用热阻丝，声振、阻力球等来进行的，由于运用及其他方面的困难，所以不能普通地使用。
