Questions A19-21

19. Hierarchical wastes management rules. The waste management hierarchy is a nationally and internationally accepted guide for prioritising waste management practices with the objective of achieving optimal environmental outcomes. It sets out the preferred order of waste management practices, from most to least preferred. The aim of the waste hierarchy is to extract the maximum practical benefits from products and to generate the minimum amount of waste. The proper application of the waste hierarchy can have several benefits. It can help prevent emissions of greenhouse gases, reduces pollutants, save energy, conserves resources, create jobs and stimulate the development of green technologies

Prevention - preventing and reducing waste generation. Reuse and preparation for reuse - giving the products a second life before they become waste. Recycle - any recovery operation by which waste materials are reprocessed into products, materials or substances whether for the original or other purposes. It includes composting and it does not include incineration. Recovery - some waste incineration based on a political non-scientific formula that upgrades the less inefficient incinerators. Disposal - processes to dispose of waste be it landfilling, incineration, pyrolisis, gasification and other finalist solutions.

20. List and briefly characterize conventional and renewable energy sources. Conventional - energy that has been used from ancient times is known as conventional energy. Conventional energy sources have a number of advantages, including being affordable, easy to harness, producing a lot of power and easy distribution. However, these sources of energy also have a downside since they may cause environmental harm as they are being used.  Coal - this is a substance that is normally formed from organic materials that died ages ago and were subjected to high quantities of pressure and heat. Coal can be used to generate electricity or to power machines like steamships.  Natural gas - when various plant and animal remains are exposed to frequent heat and pressure over thousands of years, they become natural gas. It can be used to produce electricity and for cooking.  Nuclear power - when uranium atoms are split through a process called fission, the result is production of steam or nuclear energy. This energy is normally used to generate electricity.  Oil - as with coal and natural gas, oil is formed when organic materials are subjected to heat and pressure over a long period of time. Oil is often used in powering vehicles, producing electricity and domestic heating. Non-conventional is energy that is collected from renewable resources, which are natural. The conventional energy sources discussed above are exhaustible and in some cases, installation of plants to get energy is highly expensive. In order to meet the energy demand of increased population, the scientists developed alternate nonconventional natural Resources sources of energy which should be renewable and provide a pollution free environment.     

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Solar Energy - a primary energy source, is non-polluting and inexhaustible. Hydro-electric power - dams in rivers Wind power - wind energy can be converted into mechanical or electrical energy using suitable devices. Tidal power - The energy associated with the tides of the Ocean can be converted in to electrical energy Geothermal power - The geothermal energy may be defined as the heat energy obtainable from hot rocks present inside the earth crust. At the deeper region of earth crust, the solid rock gets melted in to magma, due to very high temperature. The magma layer is pushed up due to some geological changes and get concentrated below the earth crust. The places of hot magma concentration at fairly less depth are known as hot spots. Biomass - The organic matters originated from living organisms (plants and animals) like wood, cattle dung, sewage, agricultural wastes etc. are called as biomass. These substances can be burnt to produce heat energy which can be used in the generation of

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electricity. Thus, the energy produced from the biomass is known as biomass energy. Biogas - is an important source of energy to meet energy, requirements of rural area. The gas is generated by the action of bacteria on cow dung in absence of air (oxygen).

21. What is the moment of the force F with respect to the point O? The Moment of a force is a measure of its tendency to cause a body to rotate about a specific point or axis The force F with respect to the point O is the product of the distance from the point to the point of application of the force and the component of the force perpendicular to the line of the distance The moment of a force about a point O is defined as the vector product

where

=x +y +z

is the radius vector (position vector) drawn from O to the point of

application A of the force , and = Fx + Fy + Fz is the force vector acting on A. Both vectors are expressed by their components (x, y, z) and (Fx, Fy, Fz), respectively, in Cartesian coordinate system.

Moment of the force F about the point O