To test for mechanical contact in immersed systems, experiments are done for a ball falling under gravity using an electrical set-up. A conducting sphere is dropped on a conducting plate from a given height and a voltage is applied between them. When the sphere makes or breaks electrical contact with the plate, the circuit closes or opens. The experiments done not only finds the answer of open question of contact or no contact but also tries to answer questions related to nature of the contact and the dissipation during such contacts.

We are currently conducting experiments to measure optically and interferometrically the dynamics of a sphere until sub-micrometer scale preceding the normal collision. In first phase, we tried to track a small dot on the sphere while falling under gravity and impacting the bottom wall using a high speed camera. The dynamics observed, till few micrometers, showed finite deviation from lubrication theory. Currently, we are working on observing this dynamics in sub-micrometer range using Newton rings methodology.