Torsion (mechanics) in the context of "Torque"

A siege engine is a device that is designed to break or circumvent heavy castle doors, thick city walls and other fortifications in siege warfare. Some are immobile, constructed in place to attack enemy fortifications from a distance, while others have wheels to enable advancing up to the enemy fortification. There are many distinct types, such as siege towers that allow foot soldiers to scale walls and attack the defenders, battering rams that damage walls or gates, and large ranged weapons (such as ballistas, catapults/trebuchets and other similar constructions) that attack from a distance by launching heavy projectiles. Some complex siege engines were combinations of these types.

Siege engines are fairly large constructions – from the size of a small house to a large building. From antiquity up to the development of gunpowder, they were made largely of wood, using rope or leather to help bind them, possibly with a few pieces of metal at key stress points. They could launch simple projectiles using natural materials to build up force by tension, torsion, or, in the case of trebuchets, human power or counterweights coupled with mechanical advantage. With the development of gunpowder and improved metallurgy, bombards and later heavy artillery became the primary siege engines.

A catapult is a ballistic device used to launch a projectile at a great distance without the aid of gunpowder or other propellants – particularly various types of ancient and medieval siege engines. A catapult uses the sudden release of stored potential energy to propel its payload. Most convert tension or torsion energy that was more slowly and manually built up within the device before release, via springs, bows, twisted rope, elastic, or any of numerous other materials and mechanisms which allow the catapult to launch a projectile such as rocks, cannon balls, or debris.

During wars in the ancient times, the catapult was usually known to be the strongest heavy weaponry. In modern times the term can apply to devices ranging from a simple hand-held implement (also called a "slingshot") to a mechanism for launching aircraft from a ship.

Topology (from the Greek words τόπος, 'place, location', and λόγος, 'study') is the branch of mathematics concerned with the properties of a geometric object that are preserved under continuous deformations, such as stretching, twisting, crumpling, and bending; that is, without closing holes, opening holes, tearing, gluing, or passing through itself.

A topological space is a set endowed with a structure, called a topology, which allows defining continuous deformation of subspaces, and, more generally, all kinds of continuity. Euclidean spaces, and, more generally, metric spaces are examples of topological spaces, as any distance or metric defines a topology. The deformations that are considered in topology are homeomorphisms and homotopies. A property that is invariant under such deformations is a topological property. The following are basic examples of topological properties: the dimension, which allows distinguishing between a line and a surface; compactness, which allows distinguishing between a line and a circle; connectedness, which allows distinguishing a circle from two non-intersecting circles.

The onager (UK: /ˈɒnədʒə/, /ˈɒnəɡə/; US: /ˈɑːnədʒər/) was a Roman torsion-powered siege engine. It is commonly depicted as a catapult with a bowl, bucket, or sling at the end of its throwing arm. The onager was first mentioned in 353 AD by Ammianus Marcellinus, who described onagers as the same as a scorpion. The onager is often confused with the later mangonel, a "traction trebuchet" that replaced torsion powered siege engines in the 6th century AD.

A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power, torque, and rotation, usually used to connect other components of a drivetrain that cannot be connected directly because of distance or the need to allow for relative movement between them.

As torque carriers, drive shafts are subject to torsion and shear stress, equivalent to the difference between the input torque and the load. They must therefore be strong enough to bear the stress, while avoiding too much additional weight as that would in turn increase their inertia.

A torsion spring is a spring that works by twisting its end along its axis; that is, a flexible elastic object that stores mechanical energy when it is twisted. When it is twisted, it exerts a torque in the opposite direction, proportional to the amount (angle) it is twisted. There are various types:

• A torsion bar is a straight bar of metal or rubber that is subjected to twisting (shear stress) about its axis by torque applied at its ends.
• A more delicate form used in sensitive instruments, called a torsion fiber consists of a fiber of silk, glass, or quartz under tension, that is twisted about its axis.
• A helical torsion spring, is a metal rod or wire in the shape of a helix (coil) that is subjected to twisting about the axis of the coil by sideways forces (bending moments) applied to its ends, twisting the coil tighter.
• Clocks use a spiral wound torsion spring (a form of helical torsion spring where the coils are around each other instead of piled up) sometimes called a "clock spring" or colloquially called a mainspring. Those types of torsion springs are also used for attic stairs, clutches, typewriters and other devices that need near constant torque for large angles or even multiple revolutions.

The second moment of area, or second area moment, or quadratic moment of area and also known as the area moment of inertia, is a geometrical property of an area which reflects how its points are distributed with regard to an arbitrary axis. The second moment of area is typically denoted with either an ${\displaystyle I}$ (for an axis that lies in the plane of the area) or with a ${\displaystyle J}$ (for an axis perpendicular to the plane). In both cases, it is calculated with a multiple integral over the object in question. Its dimension is L (length) to the fourth power. Its unit of dimension, when working with the International System of Units, is meters to the fourth power, m, or inches to the fourth power, in, when working in the Imperial System of Units or the US customary system.

In structural engineering, the second moment of area of a beam is an important property used in the calculation of the beam's deflection and the calculation of stress caused by a moment applied to the beam. In order to maximize the second moment of area, a large fraction of the cross-sectional area of an I-beam is located at the maximum possible distance from the centroid of the I-beam's cross-section. The planar second moment of area provides insight into a beam's resistance to bending due to an applied moment, force, or distributed load perpendicular to its neutral axis, as a function of its shape. The polar second moment of area provides insight into a beam's resistance to torsional deflection, due to an applied moment parallel to its cross-section, as a function of its shape.