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Published byMoses Ball Modified over 9 years ago
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The force applied divided by the surface area Pressure = Force/Area Force (or weight) of an object depends on its mass and the pull of gravity Area – the total surface of an object Length (m) x width (m) Unit used is meter squared (m 2 )
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As force increases, pressure also increases – directly proportional As area increases, pressure decreases – indirectly proportional
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Why???
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Just like pressure is exerted on your foot- gas molecules exert pressure on things too. Pressure can be measured in many different units: Inches of mercury Pounds per square inch (psi) Millimeters of mercury (mmHg) Atmospheres (atm) That’s a lot of different units for one thing!!
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Certain units are used in scientific measurements International System of Units (SI) – lets scientists all over the world to communicate with each other. Chart
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Certain units are used in scientific measurements International System of Units (SI) – lets scientists all over the world to communicate with each other. Chart There are 2 different “kinds” of units: - Base Units - Derived Units
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Base Units – There are 7!! basic physical measurements (units in the metric system) Ex: mass and length Derived units – Must be figured out mathematically Ex: area, force, volume and pressure
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Force is measured in Newtons (N) A bar of soap pushes down with about 1N of force. Pressure is measured in Pascals (Pa) Pascal (Pa) = N/m 2 To find pressure need 2 things: 1. Force (units = N) 2. Area (units = m 2 )
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Photo shows two bricks of the same mass lying on the ground. 1. Is each brick exerting the same total force on the ground? Explain. 2. Is each brick exerting the same pressure on the ground? Explain.
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Determine the area of the brick on the right side of the photo in Figure 2.7. The dimensions of the brick surface touching the ground are 9.3 cm × 5.5 cm. ** Remember we want to have the units in meters(m)! So we will need to convert cm m.
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