2003年高考物理(江苏卷)试题中有这样一道题目:当物体从高空下落时,空气阻力随速度的增大而增大,因此经过一段距离后将匀速下落,这个速度称为此物体下落的终极速度,已知球形物体速度不大时所受的空气阻力正比于速度v,且正比于球半径r,即阻力为f=krv,k是比例系数,对于常温下的空气,比例系数k=3.4×10~(-4)N·s/m~2,已知水的密度ρ=1.0×10~3kg/m~3,取重力加速度g=10m/s~2.试求半径r=0.1mm In the 2003 college entrance examination physics (Jiangsu volume) question, there was such a problem: When an object falls from a high altitude, the air resistance increases with the speed, so after a certain distance will fall at a uniform speed, this speed is called the fall of this object The ultimate speed, known air object resistance is not proportional to the velocity v, and is proportional to the ball radius r, that is, the resistance is f = krv, k is a proportional coefficient, for the air at room temperature, the proportional coefficient k = 3.4×10~(-4)N·s/m~2, Known water density ρ=1.0×10~3kg/m~3, take gravity acceleration g=10m/s~2. Try radius r=0.1 Mm