Can a falling ball lose speed?

TL;DR

This paper investigates how a falling ball's speed initially increases beyond its final terminal velocity due to insufficient air resistance, then decreases to stabilize at a limiting velocity caused by turbulent wake formation.

Contribution

It explains the dynamic process of speed variation in a falling ball, emphasizing the role of turbulent wake formation in reaching terminal velocity.

Findings

Ball speed surpasses final velocity before wake formation.

Turbulent wake causes the ball to slow down to terminal velocity.

Friction force from air vortices stabilizes the speed.

Abstract

A small and light polystyrene ball is released without initial speed from a certain height above the floor. Then, it falls on air. The main responsible for the friction force against the movement is the wake of successive air vortices which form behind (above) the falling ball, a turbulent phenomenon. After the wake appears, the friction force compensates the Earth gravitational attraction and the ball speed stabilises in a certain limiting value Vl. Before the formation of the turbulent wake, however, the friction force is not strong enough, allowing the initially growing speed to surpass the future final value Vl. Only after the wake finally becomes long enough, the ball speed decreases and reaches the proper Vl.