船在水中航行要受到水的阻力;飞机、汽车、摩托车以及其他物体在空气中运动,都要受到空气的阻力。试验表明,正面面积(物体垂直于运动方向的最大截面面积)相同的一切形状不同的物体,在空气或液体中以相同的速度运动时,流线体受到的阻力最小。流线体的形状是:前面圆,后面尖,表面尽可能光滑,没有凹凸不平之处,略像水滴。飞艇、潜水艇、鱼雷、竞赛汽 When a ship sails in water, it is subject to water resistance; aircraft, cars, motorcycles, and other objects moving in the air must be subjected to air resistance. Tests have shown that when all objects of different shapes with the same frontal area (maximum cross-sectional area perpendicular to the direction of motion) are moving at the same speed in the air or in the liquid, the streamlined body has the least resistance. The shape of the streamlined body is: the front circle, behind the sharp, the surface is as smooth as possible, there is no uneven place, slightly like a drop of water. Airships, submarines, torpedoes, racing cars