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Lecture

Rotational Motion: Inertia and Acceleration

In course

PHYS-101(j): General physics : mechanics

Le but du cours de physique générale est de donner à l'étudiant les notions de base nécessaires à la compréhension des phénomènes physiques. L'objectif est atteint lorsque l'étudiant est capable de prévoir quantitativement les conséquences de ces phénomène ...

Description

This lecture covers the concepts of rotational motion, inertia, and acceleration. Starting with the safety precautions for dangerous experiments, the instructor explains the calculation of moments of inertia and provides examples of objects in rotational motion. The lecture also delves into the stability of gyroscopes and practical applications of rigid bodies. Through detailed examples, students learn how to calculate accelerations and moments of inertia for various objects, such as wheels and thin rods. The discussion extends to understanding the forces involved in rotating objects and how they affect stability and motion.

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Instructors (2)

Yves Revaz

Yves Revaz is a scientist at LASTRO/EPFL. After successful studies in physics at EPFL, he accomplished his PhD entitled: "Dynamics of external regions of spiral galaxies and constraints on the dark matter", at the Geneva Observatory in the galactic dynamics group of Prof. D. Pfenniger. He then moved to the Paris Observatory to work at the LERMA (Laboratory for Studies of Radiation and Matter in Astrophysics) under the supervision of Prof. F. Combes on the understanding of cooling flows in galaxy clusters. He joined LASTRO at EPFL in 2007, where, in collaboration with Pascale Jablonka, he developed a new TreePM/SPH chemo-dynamical code called GEAR, designed to study the chemical evolution of galaxies. His current main research focus on the evolution of dwarf spheroidal galaxies and their link with the cosmology. Yves Revaz is also the author of pNbody, a parallelized python toolbox designed to manipulate large N-body systems.

Jean-Paul Richard Kneib

Official source

Ontological neighbourhood

Physics

Mechanics: Classical mechanics

Related concepts (32)

Inertia

Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law of motion. After some other definitions, Newton states in his first law of motion: LAW I. Every object perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon.

Rotation

Rotation or rotational motion is the circular movement of an object around a central line, known as axis of rotation. A plane figure can rotate in either a clockwise or counterclockwise sense around a perpendicular axis intersecting anywhere inside or outside the figure at a center of rotation. A solid figure has an infinite number of possible axes and angles of rotation, including chaotic rotation (between arbitrary orientations), in contrast to rotation around a axis.

Moment of inertia

The moment of inertia, otherwise known as the mass moment of inertia, angular mass, second moment of mass, or most accurately, rotational inertia, of a rigid body is a quantity that determines the torque needed for a desired angular acceleration about a rotational axis, akin to how mass determines the force needed for a desired acceleration. It depends on the body's mass distribution and the axis chosen, with larger moments requiring more torque to change the body's rate of rotation.

Rigid rotor

In rotordynamics, the rigid rotor is a mechanical model of rotating systems. An arbitrary rigid rotor is a 3-dimensional rigid object, such as a top. To orient such an object in space requires three angles, known as Euler angles. A special rigid rotor is the linear rotor requiring only two angles to describe, for example of a diatomic molecule. More general molecules are 3-dimensional, such as water (asymmetric rotor), ammonia (symmetric rotor), or methane (spherical rotor).

Rigid body

In physics, a rigid body, also known as a rigid object, is a solid body in which deformation is zero or negligible. The distance between any two given points on a rigid body remains constant in time regardless of external forces or moments exerted on it. A rigid body is usually considered as a continuous distribution of mass. In the study of special relativity, a perfectly rigid body does not exist; and objects can only be assumed to be rigid if they are not moving near the speed of light.

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