Impact force measurement of a spherical body dropping onto a water surface.

We propose a method for measuring the impact force of a spherical body dropping onto a water surface. The velocity of the center of gravity of a metal spherical body, in which a cube corner prism is embedded so that its optical center coincides with the center of gravity of the sphere, is accurately measured using an optical interferometer. The acceleration, displacement, and inertial force of the sphere are calculated from the velocity. The sphere is also observed using a high-speed camera. The uncertainty in measuring the instantaneous value of the impact force with a sampling interval of approximately 1 ms is estimated to be 8 mN, which corresponds to 0.8% of the maximum force of approximately 1.0 N.