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Angular Momentum: Single Particle

Angular Momentum: Single Particle

Angular momentum is directed perpendicular to the plane of the rotation, and its magnitude depends on the choice of the origin. The perpendicular vector joining the linear momentum vector of an object to the origin is called the “lever arm.” If the lever arm and linear momentum are collinear, then the magnitude of the angular momentum is zero. Therefore, in this case, the object rotates about the origin such that it lies on the rim of the circumference defined by the lever arm magnitude.
The...

Conservation of Angular Momentum

Conservation of Angular Momentum

A system's total angular momentum remains constant if the net external torque acting on the system is zero. Considering a system that consists of n tiny particles, the angular momentum of any tiny particle may change, but the system's total angular momentum would remain constant. The principle of conservation of angular momentum only considers the net external torque acting on the system. While there are internal forces exerted by different particles within the system that also produce internal...

Conservation of Angular Momentum: Application

Conservation of Angular Momentum: Application

A system's total angular momentum remains constant if the net external torque acting on the system is zero. Examples of such systems include a freely spinning bicycle tire that slows over time due to torque arising from friction, or the slowing of Earth's rotation over millions of years due to frictional forces exerted on tidal deformations. However in the absence of a net external torque, the angular momentum remains conserved. The conservation of angular momentum principle requires a change...

Rolling Without Slipping

Rolling Without Slipping

People have observed the rolling motion without slipping ever since the invention of the wheel. For example, one can look at the interaction between a car's tires and the surface of the road. If the driver presses the accelerator to the floor so that the tires spin without the car moving forward, there must be kinetic friction between the wheels and the road's surface. If the driver slowly presses the accelerator, causing the car to move forward, the tires roll without slipping. It is essential...

Angular Momentum

Angular Momentum

Angular momentum characterizes an object's rotational motion and is defined as the moment of its linear momentum about a specified point O. When a particle moves along a curved path in the x-y plane, the scalar formulation calculates the magnitude of its angular momentum, utilizing the moment arm (d), representing the perpendicular distance from point O to the line of action of the linear momentum. Despite being scalar in formulation, angular momentum is inherently a vector quantity. Its...

Torque Free Motion

Torque Free Motion

The torque-free motion refers to the movement of a rigid body in space when no external torques are acting upon it. This type of motion can be observed in environments where there are no external forces or frictions, like in outer space. For example, a rotation of Mars in space is a torque-free motion. Mars is an axisymmetric object, meaning it has an axis of symmetry along which it rotates, designated as the z-axis. The rotating frame of reference is defined such that the center of mass of...

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Related Experiment Video

Updated: Jul 10, 2026

Analyzing the Movement of the Nauplius 'Artemia salina' by Optical Tracking of Plasmonic Nanoparticles

Analyzing the Movement of the Nauplius 'Artemia salina' by Optical Tracking of Plasmonic Nanoparticles

Published on: July 15, 2014

How did venus lose its angular momentum?

Science (New York, N.Y.)

|December 11, 1970

Summary

This summary is machine-generated.

Venus likely had a fast, prograde spin but captured a moon. This event despun the planet, causing volcanism and releasing gases, explaining Venus's current slow, retrograde rotation.

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Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

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Scattering And Absorption of Light in Planetary Regoliths

Scattering And Absorption of Light in Planetary Regoliths

Published on: July 1, 2019

Related Experiment Videos

Last Updated: Jul 10, 2026

Analyzing the Movement of the Nauplius 'Artemia salina' by Optical Tracking of Plasmonic Nanoparticles

Analyzing the Movement of the Nauplius 'Artemia salina' by Optical Tracking of Plasmonic Nanoparticles

Published on: July 15, 2014

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

Laboratory Drop Towers for the Experimental Simulation of Dust-aggregate Collisions in the Early Solar System

Published on: June 5, 2014

Scattering And Absorption of Light in Planetary Regoliths

Scattering And Absorption of Light in Planetary Regoliths

Published on: July 1, 2019

Area of Science:

Planetary Science
Astronomy
Geophysics

Background:

Venus currently exhibits a slow, retrograde rotation, contrasting with the expected initial prograde spin of terrestrial planets.
Solar tidal friction, the commonly accepted mechanism for rotational changes, is insufficient to account for Venus's observed angular momentum.
The planet's initial rotation is hypothesized to be prograde with a 10- to 20-hour period.

Purpose of the Study:

To propose a novel mechanism for Venus's unusual rotational state.
To explain the observed retrograde and negligible spin of Venus.
To link a specific celestial event to Venus's geological activity and atmospheric composition.

Main Methods:

Postulation of a moon capture event from a retrograde orbit.
Analysis of the angular momentum transfer during such a capture.
Modeling the energetic consequences of rotational despinning on planetary interiors.

Main Results:

A captured moon from a retrograde orbit could effectively despin Venus.
The rotational kinetic energy loss would be converted into internal heat, triggering volcanism.
This event would facilitate the release of significant amounts of volatiles, contributing to Venus's atmosphere.

Conclusions:

The capture of a moon is a plausible explanation for Venus's current slow, retrograde rotation.
This impact event provides a unified explanation for Venus's spin state, volcanism, and volatile inventory.
The moon itself would have been destroyed upon impact with the Venusian surface.