Published on: **Mar 4, 2016**

Source: www.slideshare.net

- 1. Pressure in fluidsLiquids and gases also exert pressure…..
- 2. Pressure in liquids Pressure in liquids acts equally in ALL directions, as long as the liquid is not moving.
- 3. Pressure in gases Gases also exert pressure on things around them. The atmosphere exerts about 100 000 Pa on your body! Like liquids, pressure in gases acts equally in all directions, so long as the gas is not moving.
- 4. Magdeburg hemispheres Magdeburg hemispheres demonstrate air pressure very well. When the air is sucked out, the air pressure acting on the outside will keep the spheres stuck together.
- 5. Pressure and depth Pressure in a liquid increases with depth. Think about a column of water. The force at the bottom of the column….. …….is equal to the weight of all the water above it.
- 6. Calculating Pressure The volume of water (V) is equal to the area of its base (A) multiplied by the height of the height h column (h) V=Axh area A
- 7. Calculating Pressure Force (F) The mass of the water can be calculated using the Volume and the density of the height h water: mass = A x h x r The force (F) is equal to the weight area A of the water multiplied by gravity (g): F=Axhxrxg
- 8. Calculating Pressure Finally we know that pressure, (P) is equal to the force, (F) divided by the area, (A). Axhxrx Pressure (p) = g A The area of the column cancels out, leaving us with: p=hxrxg YOU NEED TO KNOW THIS!
- 9. Calculating pressure We can use this equation for calculating pressure differences in other liquids and gases, as long as we know the density. Turn to page 168 in your text books for some example questions on pressure, (there is a worked example on page 167 to help you).