We report the results of video observations of tiny (diameter less than 100
m) near-Earth objects (NEOs) with Tomo-e Gozen on the Kiso 105 cm Schmidt
telescope. A rotational period of a tiny asteroid reflects its dynamical
history and physical properties since smaller objects are sensitive to the YORP
effect. We carried out video observations of 60 tiny NEOs at 2 fps from 2018 to
2021 and successfully derived the rotational periods and axial ratios of 32
NEOs including 13 fast rotators with rotational periods less than 60 s. The
fastest rotator found during our survey is 2020 HS7 with a rotational period of
2.99 s. We statistically confirmed that there is a certain number of tiny fast
rotators in the NEO population, which have been missed with any previous
surveys. We have discovered that the distribution of the tiny NEOs in a
diameter and rotational period (D-P) diagram is truncated around a period of 10
s. The truncation with a flat-top shape is not explained well either by a
realistic tensile strength of NEOs or suppression of YORP by meteoroid impacts.
We propose that the dependence of the tangential YORP effect on the rotational
period potentially explains the observed pattern in the D-P diagram.