A heavy funnel bobs up and down as it sinks and sometimes tips over. Why?

This is a deceptively simple set up with minimum construction. Have fun.

Problem in full

This is problem 7 of 17 for IYPT 2027

“When a long-stemmed and sufficiently heavy funnel is released vertically into water with the stem pointing downward, it undergoes a series of damped vertical oscillations while gradually sinking. Investigate the motion and stability of the sinking funnel and the conditions under which the funnel tips over.”

Specialist equipment

None for the experiment, but a clear sided water tank will help you film the phenomena.

Safety first!

• Don’t leave containers of water unattended, especially if small children could reach them.
• Try not to spill water. It can easily spoil furnishings.