Axis: An imaginary line about which a body rotates.
Axle: The centre-pin or spindle upon which a wheel revolves.
Balance wheel: The timekeeping device used in mechanical watches, mechanical toys and some clocks.
Battery: An electrical battery is one or more electrochemical cells that convert stored chemical energy into electrical energy.
A battery has two connected electrodes, one positive (a central carbon rod) and one negative (the zinc case). A chemical reaction in the surrounding electrolyte paste leaves an excess of negative electrons on the zinc. This creates an electrical current that flows to the carbon rod.
Cam: A projecting part of a wheel, adapted to impart an alternating or variable motion of any kind to another piece pressing against it, by sliding or rolling contact.
Cams produce movement by changing a circular motion into a vertical one. The motioncreated can be simple and regular or complex and irregular.
Cog: One of a series of teeth on the circumference of a wheel, which, by engaging with corresponding projections on another wheel can transmit or receive motion.
Cog-wheel: A wheel with cogs, used to transmit motion.
Clockwork: Mechanism similar to that of a clock, wheels set in motion by weights or springs.
Clockwork toys are mainly powered by a spring. For example a wind-up is operated by the turning of a key, which winds the spring mechanism up tightly, storing energy to release later. A balance wheel then controls the speed of release, ensuring that the spring releases its energy evenly and the toy moves smoothly. Circular cog-wheels convert the energy into various movements.
Crank: A portion of an axis bent at right angles, used to communicate motion.
Electricity: Electric power, as supplied to buildings, equipment, etc., from a power station or generator; a supply of electric power for domestic use.
To make an electric current flow a continuous unbroken circuit must be present – usually a loop of copper wire. There must also be an electromotive force to push the electrons that carry the charge around the circuit. Electricity has no weight, size, colour or smell. It travels at the speed of light – 186,000 miles per second.
Electrode: A conductor by means of which an electric current is made to enter or leave an object.
Friction: Friction is the force resisting the relative motion of solid surfaces, fluid layers, and / or material elements sliding against each other.
Friction toys are powered by a spring and made to move by a backwards or forwards motion along the floor. This winds up the spring mechanism tightly, storing energy. When the toy is released (or let go), the spring is set free. Most friction toys do not have a balance wheel, which means that as the spring unwinds they slow down.
Gear: A toothed wheel that works with others to alter the relation between the speed of an engine and the speed of the driven parts (e.g. wheels).
Gravity: The force that attracts a body to the centre of the earth, or towards any other physical body having mass.
When we drop something, it falls to the ground. Gravity is the force which keeps us on the ground and the moon in orbit around the earth. Galileo, an Italian scientist in the 1500s, dropped two balls of different weights from the Leaning Tower of Pisa to demonstrate that they fall at the same speed.
Gyroscope: A device consisting of a wheel or disc spinning rapidly about an axis which is itself free to alter in direction.
When a spinning top is spun, a rotational gyroscopic force is created, which keeps the top upright. As the force reduces, the spinning effect wears off and the toy eventually falls over.
Lever: A projecting arm or handle that is moved to operate a mechanism.
A lever moves on a fixed point or pivot. The force placed on one end of the lever will transfer to lift the load. The longer the lever, the greater the distance the force has to travel and therefore, the heavier the load that can be lifted.
Magnetism: A physical phenomenon produced by the motion of electric charge, which results in attractive and repulsive forces between objects.
Mass: A coherent body of matter with no definite shape.
Pulley: A wheel with a grooved rim around which a cord passes, used to raise heavy weights.
Pulleys are used to lift heavy weights. The pulley mechanisms transform a small pulling force into a much greater lifting force. The more pulleys used, the greater the weight that can be lifted.
Push: To exert force upon a body so as to move it away.
Solar: Proceeding from the sun, as light or heat.
The sun is the ultimate source of nearly all our energy. Solar cells draw on this energy. They turn heat energy from the sun into electrical energy. This process can continue as long as the sun shines. Solar power can heat water or make things move.
Steam: The vapour into which water is converted when heated.
Steam is made by heating water at a high temperature until it turns into a gas. When the liquid changes into a gas it expands. The pressure from this expansion creates the force used inside a steam engine. Steam engines revolutionised travel and manufacturing in the early 1800s with new steam-powered trains, ships and factories.
Torsion: The action of twisting, or turning something in a spiral motion.
Wind: Air in natural motion, as that moving horizontally at any velocity along the earth’s surface.
Wind is created as the sun heats our atmosphere unevenly, making some patches warmer than others. As these warm patches of air rise, colder air blows in to replace them – and we feel a wind blowing. An average wind speed of around 25 km/h is needed to harness this energy in order to produce electricity in wind farms.