A structure is a collection of elements arranged in an optimum way to support a body or an object.////The structure of an object is the orderly distribution of its essential parts . This is what gives the object its shape.///
Mass structures: These are solid, heavy and very sturdy structures,ex: walls, dams etc///.Frame structures: These structures are formed by columns and beams that act as supporting elements. Ex:the structure of a building.///Truss structures: These structures are composed of bars that form triangles .They are lightweight and sturdy.///Suspend structures:these are held in place by cables and suspenders attached to sturdy supports . Ex :tents marquees..///A force is an influencethat can deform a bod or change its movement, or produce motion in a body at rest.///Stresses are the physical demands, that a body or object must withstand when one or more external forces are applied to it.///The strenght of a material is an ability to withstand external forces without breaking:///The basic stresses: compresion; tension: bending: torsion: shear.///A body is in equilibrium when its structure remains stationary./// we say that a structure is stable when it remains in equilibrium even when a force is applied to it.///The centre of gravity is the point where the weight of an object is considered to be concentrated.///ELEMENTS THAT INCREASE RIGIDITY: Trussing: the triangle is the only figure that cannot be deformed.///A brace is a part that is positioned diagonally between two bars to conect them by forming a right angle.///Stay cables; Section:like beams and columns.///We use the word machine to describe a set of elements or parts that work to gether and use energy to perform a task and obtain a result.///Driver element: feeds energy to the machine.///Driven element: recives the force produced to the machine.///Converting and/or transmitting element: transmits and/or converts the motion from the driver element to the driver element.///Devices that transmit and/or converts motion are called mechansisms.///TIPES OF MOTION: linear motion: the objects moves in a straight line. Rotary motion: the object moves en circles. Reciprocating motion: the objects moves forwards and backwards in a straight line. Oscillating motion: the object moves backwards and forwards tracing a curve.///Motion transmission mechanisms: In this type the mechanism is fed energy from their driver element and simply transfers it to the driven element. we can class motion transmission mechanisms as: Linear transmission mechanisms: These are a type of simple machine. Ex pulleys and levers. Rotary transmission mechansisms: These incluide friction wheels, belt and pulley systems, gears, chain and spocket systems, and worm gears.///Motion conversiob mechanisms: in this type, the mechanism converts the movement from the driver element into a movement that the driven element can use.///Pulleys are used to lift heavy loads. They are wheels with a grooved rim.///Friction wheels are a set of two wheels located one next to the other. Motion is transmitted between the wheels (driver and driven) by the friction between them.///The transmission ratio (i): is the ratio between the size of the friction wheelsand the speed of rotation.///A gear is a mechanism consisting of two wheels with teeth.///Chain and sprocket systems: these systems consists of two toothed wheels separated by a distance and connected by a chain that meshes with the teeth of the two wheels.///Worm gear: this rotary transmission mechanism consists of a worm that is fitted to the driver shaft and a toothed wheel that is fitted to the driven shaft.