Scissors are types of tools used for cutting thin material which requires little force.
They are used for cutting, for example: paper, cardboard, metal foil, thin plastic, food, cloth, rope, and wire. Scissors can also be used to cut hair.
Unlike a knife, a pair of scissors consist of two pivoted blades, each called a scissor. Most types of scissors are not particularly sharp; it is primarily the shearing between the two blades which cuts. Children's scissors are even less sharp, and the blades are often protected with plastic.
Mechanically, scissors are a first-class, double-lever with the pivot acting as the fulcrum. For cutting thick or heavy material, the mechanical advantage of a lever can be exploited by placing the material to be cut as close to the fulcrum as possible. For example, if the applied force (i.e., the hand) is twice as far away from the fulcrum as the cutting location (e.g., piece of paper), the force at the cutting location is twice that of the applied force at the handles. Specialized scissors, like bolt cutters exploit leverage by having a long handle but placing the material to be cut close to the fulcrum. Scissors cut material by applying a local shear stress at the cutting location which exceeds the material's shear strength.
A ladder is a vertical or inclined set of rungs or steps. There are two types: rigid ladders that can be leaned against a vertical surface such as a wall, and rope ladders that are hung from the top. The vertical members of a rigid ladder are called beams (US) or stiles (UK). With a bit of agility, one can slide down the stiles without climbing down each rung. Rigid ladders are usually portable, but some types are permanently fixed to buildings.
A pulley (also called a sheave or block) is a wheel with a groove between two flanges around its circumference. The groove normally locates a rope, cable or belt. Pulleys are used to change the direction of an applied force, transmit rotational motion, or realize a mechanical advantage in either a linear or rotational system of motion.
Rope and pulley systems (the rope may be a light line or a strong cable) are characterized by the use of a single rope transmitting a linear motive force (in tension) to a load through one or more pulleys for the purpose of pulling the load (often against gravity.) They are often included in the list of simple machines. In a system of a single rope and pulleys, the mechanical advantage gained is ideally the number of pulleys in the system (if one pulley is used only to change the direction of the load). The tension in the rope is reduced by the mechanical advantage, while the distance (that is, the length of rope) is increased by the same proportion. Since a slender cable is more easily managed than a fat one (albeit shorter and stronger), pulley systems are often the preferred method of applying mechanical advantage to the pulling force of a winch (as can be found in a lift crane).
In practice, the more pulleys there are, the less efficient a system is. This is due to friction in the system where cable meets pulley and in the rotational mechanism of each pulley.
It is not recorded when or by whom the pulley was first developed. It is believed however that Archimedes developed the first documented block and tackle pulley system, as recorded by Plutarch. Plutarch reported that Archimedes moved an entire warship, laden with men, using compound pulleys and his own strength.
A knife is a sharp-edged (single or double edged) instrument consisting of a thin blade used for cutting and fitted with a handle. The knife can be used as a tool or a weapon. Considered by some to be one of the most useful tools of all time, its origins date as far back as two-and-a-half million years ago, as evidenced by the Olduwan tools.[1][2] Knives can be sharp or blunt. Blunt knives are not so good for cutting but can be used for spreading things like jam on bread.
The axe or ax is an ancient and ubiquitous tool that has been used for millennia to shape, split and cut wood, harvest timber, as a weapon and a ceremonial or heraldic symbol. The axe has many forms and specialized uses but generally consists of an axe head with a handle, or helve. It is considered a simple machine.
The earliest examples of axes have heads of stone with some form of wooden handle attached (hafted) in a method to suit the available materials and use. Axes made of copper, bronze, iron and steel appeared as these technologies developed.
The axe is an example of a simple machine, as it is a type of wedge, or dual inclined plane. This reduces the effort needed by the wood chopper. It splits the wood into two parts by the pression. The handle of the axe also acts as a lever allowing the user to increase the force at the cutting edge (try using an axe head without a handle and you will see what is meant) - not using the full length of the handle is known as choking the axe. For fine chopping using a side axe this sometimes a positive effect, for felling with a double bitted axe it reduces efficiency.
Generally cutting axes have a shallow wedge angle, whereas splitting axes have a deeper angle. Most axes are double beveled, i.e. symmetrical about the axis of the blade, but some specialist axes have a single bevel blade, and (usually) an offset handle that allows them to be used for finishing work without putting the user's knuckles at risk of injury. Less common today they were once an integral part of a joiner and carpenter's tool kit - not just a tool for use in forestry. A tool of similar origin is the billhook with short handle and long blade it can be used for tasks where an axe is unsuitable. However in France and Holland the billhook often replaced the axe as a joiner's bench tool.
Most modern axes have steel heads and wooden handles (typically hickory) in the USA and ash in the UK and the rest of Europe - although plastic or fiberglass handles are common. Modern axes are specialized by use, size and form. Hafted axes with short handles designed for use with one hand are often called hand axes but the term hand axe refers to axes without handles as well. Hatchets tend to be small hafted axes often with a hammer on the back side ( the poll).
Axes were frequently used in combat as they were easy to make, and the village edge tool makers were frequently the armourers to the lord of the manor in times of war.
A wheel is a circular device that is capable of rotating on its axis, facilitating movement or transportation or performing labour in machines. A wheel together with an axle overcomes friction by facilitating motion by rolling. In order for wheels to rotate a moment needs to be applied to the wheel about its axis, either by way of gravity or by application of another external force. Common examples are found in transport applications. More generally the term is also used for other circular objects that rotate or turn, such as a Ship's wheel and flywheel.
A screw is a shaft with a helical groove or thread formed on its surface and provision at one end to turn the screw. Its main uses are as a threaded fastener used to hold objects together, and as a simple machine used to translate torque into linear force. It can also be defined as an inclined plane wrapped around a shaft.
The screwpump was invented by Sennacherib (r. 705–681 BC) and improved by Archimedes (c. 287–212 BC).[1] The device is a large screw in a pipe used in antiquity and to the present day to pump liquids.
A screw may be used to move one object, with a threaded hole right through it, relative to another object to which one end of the screw is fastened allowing it to rotate but not to move axially. A vise tool is an example of this use. In effect, a wood screw also acts this way.
Because it moves forward in a screwing motion, the propeller of a ship is called a screw. Likewise, the propeller of an aircraft is called an airscrew.
