The Doomed Fly: a kinematic teaser

Article Summary

In this article we use a variety of analytical and graphical methods to determine the remaining lifespan of a doomed fly trapped between two moving walls.

Our scenario begins with two facing vertical walls 100 metres apart and the fly standing on one of the walls. At this instant the walls start to approach one another at a speed of 100 m per sec. Simultaneously, the fly takes off with a constant horizontal speed of 200 m per sec in the direction of the opposite approaching wall.

In modelling this situation, we will also make the following assumptions:

i) the fly reaches the speed of 200 m per sec instantaneously from take-off; and

ii) during its subsequent fight, whenever the fly reaches an oncoming wall, it instantaneously reverses its horizontal direction towards the other approaching wall and flies at a constant speed of 200 m per sec.

The problem is to determine the duration and total length of the fly's flight, before the fly gets unceremoniously squashed between the two walls?

You can read the full Doomed Fly article by clicking here.
Article written by:
Ian Tame
Senior Tutor