Sink to the Mark
The server picks a thick liquid (such as glycerine or castor oil), a ball material (such as steel or glass) and a target for the steady sinking speed (always achievable), you choose the ball's radius, and a real terminal-velocity model judges how fast it settles. Hitting the target refunds your run.
About this simulation
What it shows
A puzzle on a ball sinking through a thick liquid. The liquid (such as glycerine) and the ball material (such as steel) are given, along with a target for the steady sinking speed. You choose the ball's radius, then run it.
The key idea
The ball speeds up until the liquid's drag and buoyancy balance its weight, then sinks at a steady speed. In a thick liquid that speed grows with the square of the radius (v ∝ r²), so doubling the radius makes it sink about four times faster.
Try this
Run it once, see whether the ball settles too slowly or too fast, then choose a bigger ball to sink faster or a smaller one to sink slower.