FSc ICS Notes Physics XI Short Questions & Definitions Chapter 4 Work and Energy 1st Year Physics Notes Online Taleem Ilm Hub
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Work: i) The work is done on a body when it is moved or
stopped through a certain distance by the action of an applied force. ii) The product of force and component of displacement in
the direction of force.
Joule: The amount of work done, when a force of one Newton acting on a body displaces it through a distance of 1 meter along the direction of force.
Gravitation: Universal attraction between masses.
Gravitational field: The space around the earth within which it exerts a force of attraction on or near the surface of a celestial object.
Gravitational force (or Force of gravitational attraction): The mutual force of attraction which acts universally between two bodies of matter.
Conservative field: In which the work done between two points in the field is independent of the path followed between the two points.
Gravitational field: The space around the earth within which it exerts a force of attraction on other bodies.
Electric field: The region in which an electric force acts on a charge brought into the region.
Magnetic field: The region or space near a magnet where the effects of magnetism such as the deflection of a compass needle can be detected.
Elastic spring force: A weighing spring normally spiral coils, and its elongation is proportional to the applied force, so that the spring can be calibrated to measure this force.
Electric force (Electrostatic force): Force between two charged bodies. It is proportional to the product of charges, divided by the square of the distance that separates them;
F = (K(q1.q2))/r(square)
Frictional force: Tangential force exerted by a surface on a body in contact which tend to prevent or retard motion.
Propulsion force: The force to drive onward.
Conservative force: A force is conservative if the work done by that force when moving an object from one point to another is independent of the path taken between those two points; e.g. gravitational force.
Non-conservative force: The force by which work done is dependent on the path followed.
Jumbo Jet: Massive airplanes capable of carrying hundreds of passengers. e.g. Concorde commercial jet, to fly faster than the speed of sound.
Fission (or Nuclear fission): The disintegration of an atomic nucleus into two or more large fragments.
Uranium: A hard heavy, white metallic element which possesses radioactive properties, having three isotopes 92U238, 92U235, 92U234.
Ton: Any of various relatively large measures of weight.
Long ton: The weight of 2,240 pounds used in Great Britain.
Short ton: The weight of 2000 pounds used in America.
Metric ton: The weight of 2,204.6 pounds (or 1000 kg).
Power ( P ): The time rate of doing work.
Instantaneous power: The ratio of work done to the time interval, which is extremely small.
Average power: The uniform rate of doing work.
Watt : It is the power of an agency which does work at the rate of 1 joule per second.
Horsepower ( hp ): The power is said to be a hp if 550 ft-lb of work is done per second.
Energy: The ability or capacity for doing work.
Kinetic Energy: The energy possessed by a body due to its motion.
Potential energy: It is the energy possessed by a body due to its position.
Gravitational potential energy: The energy possessed by a body due to its position in the gravitational field.
Elastic potential energy: The amount of work done against the elastic force or in compressing an elastic spring.
Absolute potential energy: Energy required to move a mass from the earth up to an infinite distance.
Work-Energy Principle: Work done on the body equals change in its kinetic energy. Mathematically;
F.d = ½ m vf(2) - ½ m vi(2)
Fossil: Any trace, impression or remains of a plant or animal preserved in earth, clay, or rock from a past age.
Fossil fuel: Remains of a plant or animal preserved in earth and is used for producing heat or energy.
Escape velocity: The initial velocity, which a projectile must have at the earth’s surface in order to go out of earth’s gravitational field.
Law of conservation of energy: The total energy of a system cannot change unless energy is taken from or given to the outside. The law is equivalent to the first law of thermodynamics.
Methanol (Methyl alcohol) [CH3OH]: A colourless liquid. It is made by catalytic oxidation of methane (from natural gas) using air.
Dam: A bank or wall built so as to hold water.
Tidal energy: Electricity obtained from the power plant that uses the ‘head’ of water created by the rise and fall of the ocean tides to spin the water turbines.
Solar energy: The energy produced by nuclear fusion and comprises almost entirely electromagnetic radiation.
Solar cell: A device which converts solar energy or artificial light into electrical energy.
Photo voltaic cell: An electronic device that uses the photovoltaic effect to produce an e.m.f.
Photovoltaic effect: The production of an e.m.f. between two layers of different materials by incident electromagnetic radiation.
Electromotive force (e.m.f.): A measure of the energy supplied by a source of electric current. The unit of e.m.f. is the volt.
Satellite: A smaller body that revolves around a larger body.
Turbine: An engine in which a shaft is rotated by fluid impinging upon a system of blades or buckets mounted upon it.
Turbine generator: A generator which produces electric current with the help of turbines.
Hydroelectric plant: An electricity-generating plant powered by water falling under gravity through water turbine.
Electric generator: Machine that drives electric current when it itself is driven mechanically.
Hydal energy: Electricity produced from water power by the arrangement of machinery.
Wind energy: Mechanical energy obtained from wind mills installed in windy regions to be used in tube wells or flour mills.
Wind mills: A plant consisting of shafts to produce mechanical energy, work by the action of the wind.
Biomass energy: Energy taken from plant material or vegetation as a source of fuel.
Combustion: The act of burning, or the state of being burned.
Fermentation: A slow breaking down of organic substances (vegetable and animal origin) by yeasts and bacteria usually accompanied by evolution of heat and gas.
Organic material: A material containing carbon combined with hydrogen , and often also with oxygen, and other elements.
Fertilizer: Any material put in or on the ground , which contains plant food.
Geothermal energy: Energy generated by tapping the energy of the hot, molten areas inside the earth crust.
Methane (CH4): A colorless odorless gas. It is the simplest hydrocarbon, being the first member of the alkane series.
Nuclear energy: The energy liberated by a nuclear reaction (fission or fusion ) or by radioactive decay.
Radioactivity: The spontaneous, uncontrollable decay of an atomic nucleus with the emission of particles and gamma rays.
Radioactive: Describing an element or nuclide that exhibits natural radioactivity.
Radioactive decay: The spontaneous disintegration of unstable (radioactive) nuclei to give other a lighter more stable nuclei, accompanied by the emission of particles and/or photons.
Volcano: An opening in the earth’s surface, usually surrounded by a mass of ejected material forming a conical hill or mountain from which molten rock, fire, and steam are, or have been, exploded.
Volcanic region: The area or region in which the mass of ejected material of volcano can have affect.
Spring: A natural fountain or supply of water rising to the surface of the earth.
Hot springs: Supply or explode or discharge suddenly hot water from a spring.
Geyser: i) A natural spring that spouts a column of hot water and steam into the air at frequent and irregular intervals. ii) A hot spring which frequently throws forth jets of water, mud, etc.
Aquifer: A layer of rock holding water that allows water to pass through it with pressure.
Percolate: To pass, as a liquid, through very small spaces; as, water percolate through sand.
Magma (or lava): Semi-fluid material within the earth from which a volcanic rock results by cooling.
Catapult: A forked stick with an elastic band by which stones are thrown.
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