Investigating Forces & Motion

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INI File | 1998-02-10 | 13KB | 498 lines

[general] wordcount:72 [word1] word:acceleration def:\ The rate at which velocity changes. \ Acceleration \ has units metre per second per second (m/s▓). [word2] word:atmosphere def:\ The mixture of gases, mainly nitrogen and oxygen, \ which clings in a layer to the Earth's surface. [word3] word:barometer def:\ An instrument for measuring atmospheric pressure. [word4] word:Boyle's law def:\ A sample of gas obeys Boyle's \ law if its pressure multiplied by \ its volume is a constant at constant temperature. PV = \ constant. [word5] word:brittle def:\ In a tensile test a brittle material, for \ example glass, snaps almost as soon as its elastic limit is exceeded. [word6] word:centre of gravity def:\ The single point in a body through which its weight \ (the force of gravity acting on the body) can be considered to \ act. [word7] word:centripetal acceleration def:\ Acceleration towards the centre of a circle. The \ acceleration of an object moving at a constant speed in a circle \ is always centripetal. [word8] word:centripetal force def:\ The force directed towards the centre of a circle \ which is needed to produce centripetal \ force and maintain circular motion. [word9] word:compressive def:\ A combination of two or more forces is compressive \ if it squeezes or squashes the object on which it acts. [word10] word:contact force def:\ The force that prevents one object passing into another \ when they are in contact. Contact \ forces are produced by electrical repulsion between the atoms \ in the two objects. [word11] word:displacement def:\ Distance moved or measured in a given direction. \ Displacement is a vector quantity \ with direction as well as size. [word12] word:ductile def:\ In a tensile test , a ductile \ metal, for example copper, stretches permanently (plastically) \ when its elastic limit is exceeded. The more ductile it is, the \ further it stretches before it fractures. [word13] word:drag def:\ The force that opposes the motion of an object \ though a fluid such as air or water. [word14] word:dynamic friction def:\ The frictional forces that oppose the relative \ motion of two surfaces which are in the process of sliding over \ each other. [word15] word:elastic def:\ A material is elastic \ if it returns to its original length when the stretching force \ is removed. All materials are elastic for small loads. [word16] word:elastic limit def:\ The limit beyond which any further increase in load \ changes the shape of a material permanently. [word17] word:elastic potential energy def:\ The energy stored in, for example, a stretched spring \ or elastic rope. [word18] word:elasticity def:\ The ability of a material to be deformed by forces \ then return to its original shape when the forces are removed. [word19] word:energy def:\ The capacity to do work or bring about change. [word20] word:equilibrium def:\ An object is in equilibrium \ if the forces acting on it are exactly balanced. [word21] word:force def:\ A push or pull that tends to change the motion of \ a mass. Examples of forces include \ the forces of gravity, electricity and magnetism. [word22] word:gas def:\ The state of matter in which the atoms or molecules \ of a substance move around freely and independently of each other. \ Gases are thin, usually invisible, \ substances that expand to fill their containers. [word23] word:gradient def:\ A slope. The gradient \ of a straight line graph is calculated by dividing the increase \ in y (the variable plotted on the vertical axis) by the \ corresponding increase in x (the variable on the horizontal \ axis). [word24] word:gravitational potential energy def:\ The potential energy stored by a mass when it is \ acted on by the force of gravity. Lifting a mass m through \ height h on the Earth's surface increases its gravitational \ potential energy by mgh. \ [word25] word:gravity def:\ The attractive force that acts between all objects \ with mass. The force of gravity gives objects their weight and \ holds the planets in their orbits around the Sun. [word26] word:Hooke's law def:\ A material obeys Hooke's \ law when, in a tensile test, the extension is proportional to \ the load. [word27] word:hydraulics def:\ Hydraulic systems use liquids such as oil \ or water to transmit forces from one place to another. For example, \ hydraulic car brakes. [word28] word:impulse def:\ The impulse of a force \ is the force multiplied by the time for which it acts. Impulse \ = Ft = change in momentum. [word29] word:joule def:\ A unit of energy. One joule \ is the energy transferred when a force of one newton moves by \ a distance of one metre in the direction of the force. [word30] word:kilogram def:\ A unit of mass. A standard bag of sugar has a mass \ of 1 kilogram. [word31] word:kilometre def:\ One thousand metres. [word32] word:kinetic energy def:\ The energy that a moving mass has by virtue of its \ motion. \ Kinetic energy = ½mv▓ . [word33] word:liquid def:\ The state of matter in which the atoms or molecules \ of a substance are in close contact but tumble freely over each \ other. Liquids do not have a fixed \ shape. They flow to take the shape of their container. [word34] word:lubricant def:\ A substance such as oil that reduces the friction \ between two surfaces. [word35] word:magnitude def:\ The size of a quantity such as a vector or a number, \ without reference to its direction or sign. [word36] word:manometer def:\ An instrument for measuring pressure which consists \ of a U shape tube partly filled with liquid. [word37] word:mass def:\ Mass can be thought of as the 'amount of \ matter in an object'. The mass of an object determines how rapidly \ it accelerates when it is acted on by a force, and the strength \ of its gravitational attraction to other objects. [word38] word:metre def:\ The unit of length. [word39] word:micrometer def:\ A measuring instrument for measuring very small lengths. [word40] word:micrometre def:\ One millionth of a metre. [word41] word:moment of force def:\ The turning effect of a force. Also known as torque. \ The moment of the force about a point \ is the product of the force, and the perpendicular distance from \ the point to the line along which the force acts. [word42] word:momentum def:\ The product of the mass and the velocity of a moving \ object. Momentum = mass x velocity. [word43] word:newton def:\ The unit of force. One newton \ is the force that gives a mass of one kilogram an acceleration \ of one metre per second per second. [word44] word:orbit def:\ The path of a satellite around a star or planet. \ Orbits are circular or elliptical (like \ stretched circles). [word45] word:parabola def:\ A particular mathematical curve. The path followed \ by a projectile is a parabola. [word46] word:pascal def:\ The unit of pressure. One pascal \ is equal to a pressure of one newton per square metre. 1 Pa = 1 \ N/m▓. [word47] word:plastic def:\ A material is plastic \ if its shape is changed permanently when it is stretched or deformed \ in some other way by forces. Materials such as polythene are called \ 'plastics' because they can undergo considerable plastic changes \ in shape. [word48] word:potential energy def:\ The energy an object has by the virtue of forces \ (for example gravitational or electrical forces) acting on it \ or within it. [word49] word:power def:\ The rate at which work is done or energy is transferred. \ Power = energy transferred/time. [word50] word:pressure def:\ The pressure on a surface \ is the force per unit area acting perpendicular to the surface. \ \ Pressure = force/area. [word51] word:projectile def:\ A projectile is an object, \ for example a golf ball, launched horizontally or at an angle \ to the horizontal. The acceleration due to gravity, which always \ points vertically downwards, makes the projectile follow a parabolic \ path or 'trajectory'. [word52] word:reaction force def:\ For every force there is an equal and opposite \ reaction force. The 'action' and the 'reaction' forces always \ act on different objects. The contact force which prevents one \ object passing through another when they are pushed together, \ is often described as a reaction force. [word53] word:resultant def:\ The resultant of two \ forces acting together is a single force that produces the same \ acceleration. The resultant is found by adding the forces together \ and taking proper account of their direction. For example the \ resultant of two equal but opposite forces is zero. [word54] word:rubber def:\ A natural material that can be stretched elastically \ to several times its unstretched length. [word55] word:scalar def:\ A quantity such as mass, or speed which has a size \ but does not have a direction. [word56] word:seismograph def:\ An instrument used to record the Earth's vibrations, \ especially those produced by earthquakes. [word57] word:shearing def:\ The action of a pair of equal and opposite forces \ acting on opposite sides of an object, making one side slip or \ slide relative to the other. [word58] word:speed def:\ The rate at which distance is travelled. Speed \ = distance/time. [word59] word:static friction def:\ The frictional forces that oppose the relative motion \ of two stationary surfaces which are just on the point of sliding \ over each other. [word60] word:streamlining def:\ Shaping a vehicle or other object so that air or \ water flows past it smoothly producing as little drag as possible. [word61] word:strength def:\ The maximum load that a material can support before \ it fractures. [word62] word:tensile test def:\ A test in which a material is stretched by a load \ and the resulting extension is measured. The results of the test \ are recorded as a graph of load against extension. [word63] word:terminal velocity def:\ The steady velocity with \ which an object falls, following its initial acceleration, through \ a fluid. Terminal velocity is reached when drag forces exactly \ balance the object's weight. [word64] word:torque def:\ The turning effect of a force. Also known as the \ moment of the force. The moment of the force about a point is \ the product of the force, and the perpendicular distance from \ the point to the line along which the force acts. [word65] word:vector def:\ A quantity such as velocity or force that has both \ size and direction. [word66] word:velocity def:\ Speed in a particular direction. Velocity \ is a vector quantity with direction as well as size. Can also \ be defined as the rate of change of displacement. [word67] word:watt def:\ The unit of power. One watt \ is equal to a rate of energy transfer of one joule per second. [word68] word:weight def:\ The force of gravity on a mass, particularly at the \ surface of the Earth (or any other planet). On the Earth weight \ = mg, where g is the acceleration due to gravity at the \ Earth's surface. [word69] word:weightless def:\ A mass is weightless \ when it is in space, distant from any other masses. Masses also \ behave as if they are weightless when they are in 'free-fall', \ for example, inside a spacecraft orbiting the Earth. [word70] word:work def:\ Work is done when a force moves through a \ distance in the direction of the force. For example, when you push \ a swing you do work which increases the energy of the swing. The \ unit of work is that of energy - joule. [word71] word:work hardening def:\ When a metal is deformed plastically it becomes \ harder and more liable to crack. For example you can work harden \ a wire paper clip by bending it to and fro. [word72] word:yield point def:\ The load in a tensile test at which a specimen 'yields' \ and begins to stretch permanently.