1. Done by: Andrew Ong 3P316

2. The symbol for Pressure is P ( Pascal) Definition: The force per unit area applied in a direction perpendicular to the surface of an object.

3. The SI unit for pressure is the Pascal (Pa), equal to one Newton per square meter. This special name for the unit was added in 1971; before that, pressure in SI was expressed simply as N/m2.

4. One example which shows the application of pressure can be seen in a knife. By cutting a fruit with the flat side of the knife, we are unable to cut the fruit. However, if we use the thin side of the knife to cut the fruit, we are able to cut it easily. This is because the flat side has a greater surface area, which means less pressure, and hence is unable to cut the fruit. However, when using the thin side, the surface area is smaller and thus it cuts the fruit easily and smoothly.

5. Other applications Some other applications of pressure can be seen with the following examples:

6. Pressure of solid on a solid For example, if you push on an object with your hand with a force of 20 pounds, and the area of your hand is 10 square inches, then the pressure you are exerting is 20 / 10 = 2 pounds per square inch.

7. Pressure of solid on a solid Pressure equals Force divided by Area You can see that for a given force, if the surface area is smaller, the pressure will be greater. If you use a larger area, you are spreading out the force, and the pressure (or force per unit area) becomes smaller.

8. Solid pressing on confined fluid When a liquid or gas is confined in a container or cylinder, you can create a pressure by applying a force with a solid piston. The pressure created in the cylinder equals the force applied divided by the area of the piston: P = F/A.

9. Solid pressing on confined fluid In a confined fluid—the pressure is equal throughout the container, pressing equally on all the surrounding walls. In the example of a bicycle pump, the pressure created inside the pump will be transmitted through the hose into the bicycle tire. Pressure is in all directions in a fluid Increasing the force will increase the pressure inside the cylinder.

10. Caused by gravity In special cases, since the weight of an object is a force caused by gravity, we can substitute weight in the pressure equation. Thus the pressure (P) caused by the weight (W) of an object is that weight divided by the area (A) where the weight is applied. P = W/A

11. Caused by gravity If you place a solid object on the floor, the pressure on the floor over the area of contact is the weight of the object divided by the area on the floor.

12. Formula P is the pressure F is the normal force A is the area. P=F/A or P=dF/dA

13. Hydrostatic Pressure Hydrostatic pressure is the pressure exerted by a fluid at equilibrium due to the force of gravity It can be determined from a control volume analysis of an infinitesimally small cube of fluid

14. Hydrostatic Pressure Hydrostatic pressure can be calculated according to the following formula: p is the hydrostatic pressure (Pa), ρ is the fluid density (kg/m3), g is gravitational acceleration (m/s2), A is the test area (m2), z is the height (parallel to the direction of gravity) of the test area (m), z0 is the height of the zero reference point of the pressure (m).

15. Atmospheric pressure Statistical mechanics shows that, for a gas of constant temperature, T, its pressure, p will vary with height, h, as: P(h)=p(0)e^ -Mgh/kT where: –g = the acceleration due to gravity –T = Absolute temperature (i.e. kelvins) –k = Boltzmann constant –M = mass of a single molecule of gas –p = pressure –h = height

16. Atmospheric pressure If there are multiple types of molecules in the gas, the partial pressure of each type will be given by this equation. Under most conditions, the distribution of each species of gas is independent of the other species.

17. Buoyancy Any body of arbitrary shape which is immersed, partly or fully, in a fluid will experience the action of a net force in the opposite direction of the local pressure gradient. If this pressure gradient arises from gravity, the net force is in the vertical direction opposite that of the gravitational force. This vertical force is termed buoyancy or buoyant force and is equal in magnitude, but opposite in direction, to the weight of the displaced fluid.

18. Buoyancy In the case of a ship, for instance, its weight is balanced by a buoyant force from the displaced water, allowing it to float. If more cargo is loaded onto the ship, it would sink more into the water - displacing more water and thus receive a higher buoyant force to balance the increased weight. The person who discovered buoyancy is Archimedes.

19. Bibliography References: http://en.wikipedia.org/wiki/Pressure#Form ulahttp://en.wikipedia.org/wiki/Pressure#Form ula http://en.wikipedia.org/wiki/Pressure http://en.wikipedia.org/wiki/Fluid_statics Pictures: http://www.google.com.sg/pictures