A small raindrop of mass falls vertically through still air
PHYSICS · Multi-part · ISC · Physics · Properties of Bulk Matter · Properties of Bulk Matter
Problem
A small raindrop of mass 3.0mg falls vertically through still air. After a short distance it attains a constant terminal speed. The viscous drag force acting on the drop is proportional to its speed and may be written as Fd=kv, where k=1.2×10−4N s m−1.
(i) Draw a free-body diagram for the raindrop when it is falling with terminal speed.
(ii) Taking the downward direction as positive, write the force balance equation for the drop at terminal speed and hence show that its terminal speed vt is given by vt=kmg.
(iii) Calculate the numerical value of the terminal speed of the drop. Take g=9.8m s−2.