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| Pressure |
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| There are many situations in which effects of a force are better described in terms of force per unit area i.e. pressure. |
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| Example |
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 Pins and nails have pointed ends so that, when a pin is pressed, high pressure is applied on the surface with lesser force, as area is small. |
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 Tractors with wide wheels can move over soft ground because their weight (force of gravity) is spread over a large area and so that the tractors do not sink. |
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 Bags and suitcases are provided with broad handles so that a small pressure is exerted on the hands. |
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 Railway tracks are laid on large concrete sleepers so that the pressure on the ground is reduced, which would otherwise, yield to weight of trains. |
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S.I unit of pressure is  or Pascal (Pa) and its dimensional formula is [ML-1T-2
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| Consider a liquid of density 'r' contained in a cylinder of cross-sectional area 'A'. Let 'h' be the height of the liquid column. The weight of liquid will exert a downward thrust on the bottom surface of the vessel. The weight of liquid inside the vessel = volume x density x g = Ahrg |
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| Thrust or force of liquid on the area = weight of liquid = Ahrg |
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| Pressure exerted by a liquid column = hrg |
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| The above expression tells us why dams are broader at the bottom. The liquid pressure increases with breadth. |
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| With a broader base, the pressure on the walls of the dam are reduced. |
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