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Types of mechanical forces

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A force exerted on a body can cause a change in either the shape or the motion of the body.The unit of force in SI system is the Newton(N) and CGS system is dyne.No solid body is perfectly rigid and when force are applied to it,changes in dimension occur.such changes are not always perceptible to the human eye since they are negligible. For the example,The span of a bridge will sag under the weight of a vehicle and a spanner will bend slightly when tightening a nut. It is also important for civil engineers and designers to appreciate the effects of forces on materials.Together with their mechanical properties of the materials. There three main types of mechanical forces that can act on a body.They are 1)Tensile force 2) compressive force and 3) shear force
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What is specific gravity and examples with diagrams.

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Specific gravity is the ratio of the density of a substance to the density of a reference substance; equivalently, it is the ratio of the mass of a substance to the mass of a reference substance for the same given volume. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water at its densest (4°C) for liquids; for gases it is air at room temperature (21°C). Nonetheless, the temperature and pressure must be specified for both the sample and the reference. Pressure is nearly always 1 atm (101.325 kPa). Temperatures for both sample and reference vary from industry to industry. In British beer brewing, the practice for specific gravity as specified above is to multiply it by 1000.[1] Specific gravity is commonly used in industry as a simple means of obtaining information about the concentration of solutions of various materials such as brines, hydrocarbons, sugar solutions (syrups, juices, honeys, brewers wort, must etc.) and acids

EXAMPLES:

  • Helium gas has a density of 0.164g/liter[8]It is 0.139 times as dense as air.
  • Air has a density of 1.18g/l[8]
MaterialSpecific Gravity
Balsa wood0.2
Oak wood0.75
Ethanol0.78
Water1
Table salt2.17
Aluminium2.7
Cement3.15
Iron7.87
Copper8.96
Lead11.35
Mercury13.56
Depleted uranium19.1
Gold19.3
Osmium22.59
(Samples may vary, and these figures are approximate.)
  • Urine normally has a specific gravity between 1.003 and 1.035.
  • Blood normally has a specific gravity of ~1.060.

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