Dzhanibekov effect in a physics classroom

The purpose of this publication is to present a novel approach to the demonstration of the Dzhanibekov effect. The main idea of our version is to use a lightweight spinning top of a spherical external form but distinct principal moments of inertia floating in the upward flow of air. As a result, the Dzhanibekov effect can be easily demonstrated anywhere on Earth: in any classroom, or even in the ‘home-lab’. The proposed demonstration allows one to observe the periodical flipping motion of the asymmetrical top with the clearly seen quasi-stable rotational phase. It may also become the base for various theoretical and experimental research projects for students.

The asteroid 162173 Ryugu: a cometary origin

The Japanese Hayabusa2 mission has revealed in detail the physical characteristics of the C-type asteroid 162173 Ryugu, in particular, its spinning top-shaped rubble pile structure [1] and the potentially extremely high organic content [2,3]. A widely-accepted formation scenario for Ryugu is catastrophic collision between larger asteroids and the subsequent slow gravitational accumulation of collisional debris [4,5]. However, the collisional re-accumulation scenario does not explain the origin of the abundant organic matter. An alternative scenario is that Ryugu is an extinct comet, which lost its icy components [2,6,3]. Here, the sublimation of water ice from a uniform porous cometary nucleus was numerically simulated until the refractory components, such as silicate rocks and organic matter were left behind as evaporative residues. Such a process represents the transformation from a comet to an asteroid. The spin-up related to the shrinking nucleus, associated with the water ice sublimation, was also calculated. The result of the calculation indicates that the cometary origin scenario can quantitatively account for all the features of Ryugu discussed above. We conclude that organic-rich spinning top-shaped rubble pile asteroids, such as Ryugu, are comet-asteroid transition objects or extinct comets.

Nonlinear Stability Analysis of a Spinning Top with an Interior Liquid-Filled Cavity

Consider the motion of the the coupled system, $\mathscr S$, constituted by a (non-necessarily symmetric) top, $\mathscr B$, with an interior cavity, $\mathscr C$, completely filled up with a Navier-Stokes liquid, $\mathscr L$. A particular steady-state motion $\bar{\sf s}$ (say) of $\mathscr S$, is when $\mathscr L$ is at rest with respect to $\mathscr B$, and $\mathscr S$, as a whole rigid body, spins with a constant angular velocity $\bar{\V\omega}$ around a vertical axis passing through its center of mass $G$ in its highest position ({\em upright spinning top}). We then provide a completely characterization of the nonlinear stability of $\bar{\sf s}$ by showing, roughly speaking, that $\bar{\sf s}$ is stable if and only if $|\bar{\V\omega}|$ is sufficiently large, all other physical parameters being fixed. Moreover we show that, unlike the case when $\mathscr C$ is empty, under the above stability conditions, the top will eventually return to the unperturbed upright configuration.

Inovasi Dan Desain Turbin Hidrokinetik Darrieus Berdasarkan Bentuk Distribusi Kecepatan Aliran

Darrieus turbine use blades with a hydrofoil shape, so the rotational ability is influenced by lift force. This caused the initial rotation capability to be very low when compared to the drag turbine type. The flow velocity distribution in the vertical direction indicates a small cross-sectional speed of flow approaching the base of the flow channel, then rising towards the surface. Darrieus Spinning Top turbine is the result of innovation and design based on the concept of flow velocity distribution. Darrieus Spinning Top turbine’s blade shapes are circular-arc and straight-line, adjusting flow velocity distribution of 0.2H, 0.6H and 0.8H from the top of the turbine. In this study, a performance comparison was conducted between Darrieus turbine and Spinning Top Darrieus. Darrieus turbines produce RPM and torque values of 54.59 – 67.90 and 0.014 – 0.029 Nm, respectively. Darrieus Spinning Top turbines produce RPM values and torque of 69.24 – 82.02 and 0.012 – 0.020 Nm respectively. RPM improvements in Darrieus Spinning Top turbine design increase the influence of lift force (increased λ value). This results in a high lap rate, but requires a high self starting to perform the turbine rotation cycle.