In physics class
轮轴 names a specific simple machine - a large wheel attached to a smaller shaft, used to multiply force (think doorknob, screwdriver, ship's helm). The other five
简单机械 are
杠杆 (lever),
滑轮 (pulley),
斜面 (inclined plane),
楔子 (wedge) and
螺旋 (screw).
