P:5 Part 3

P:5 Part 3

1. Pressure in a Fluid

   • fluid is a liquid or a gas
   • as particles move around in a fluid, they collide with the surface of objects of the fluid or the surface of the container
   • the collisions create a force normal (at right-angles) to the surface
   • the link between pressure, force and area is described in the following equation:
   • if the pressure acts on a bigger area, it will produce a larger force

2. Atmospheric Pressure

   • the atmosphere is a thin layer of air around the Earth
   • the greater the altitude, the less dense the atmosphere and the lower the atmospheric pressure
   • at a high altitude, there is less air above a surface than at lower altitudes, so there is a smaller weight of air acting on the surface and the equation: pressure = force/area will result in a lower pressure

3. Pressure in a Column of Liquid

   • pressure at a particular point in a liquid depends on:
     • the height of the column above the point
     • the density of the liquid
   • the higher the column, and the denser the liquid:
     • the greater the weight above the point
     • the greater the force on the surface at that point
     • the greater the pressure
   • the pressure can be calculated with the equation:

4. Upthrust

   • when an object is submerged in a liquid, there is a greater height of liquid above the bottom surface than above the top surface
   • the bottom surface experiences more pressure and thus creates an upwards force
   • the upward force exerted by a liquid on a submerjed object is called upthrust
   • an object floats when it's weight is equal to the upthrust
   • density dertermines if an object will sink
   • an object less dense than the liquid:
     • displaces a volume of liquid greater than it's own weight so it will rise to the surface
     • will float with some of the object remaining below the surface
     • displaces liquid equal to the weight of the liquid
   • the lower an object's density, the more of it will remain above the surface

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