Transferring Pressure in a System Pressure in a fluid Calculating Pressure

Recap! What is a PNEUMATIC system? Uses gasses to do their work The gasses ARE compressible The systems can be open systems What is a HYDRAULIC system? Uses Liquids to do their work The Liquids are NOT compressible The systems are always closed systems Remember the definition of WORK… “to exert a FORCE over a DISTANCE”

First Things First!!! You are going to individually read out of the Science Focus 8 Textbook Please read pages… 304 to 305 as well as 307 and the top of 308

Pascal’s Law Pascal’s Law states that a fluid will transmit pressure equally in all directions We can see this effect if we squeeze a balloon. The balloon will bulge out in all directions We will take a plastic bottle with two holes at the same height and see what happens to the streams that leak out of each hole What are your predictions for this test… Write them down in your note book along with a little diagram of our experiment

What did we find out? We saw that the two streams that leaked out of the can both “shot” out to the same distance Page 57 and 58 This is because water pressure within the can exerted the same force in all directions The same would be seen with a compressed gas

Pascal’s Vase and Equal Pressure This vase shows that the fluid is not affected by the shape of the container Because all of the tubes are connected to the same base, the fluid is under equal pressure and therefore it levels off to the same height in each tube

Pressure within a Fluid In any fluid, whether it is compressed or not, the pressure will be equal throughout the entire fluid Fluids exert pressure equally in all directions As fluid is released from a compression container, the fluid will decompress at a steady rate

Calculating Pressure The equation to calculate pressure is: Pressure (Pa) = Force (N) Area (m²) The abbreviated form of this equation is: P = F A The equation can also be rearranged to calculate F & A F = P x A or A = F P Don’t forget the units

Example Questions If a man applies a force of 450 N to the input piston of a hydraulic jack which has a surface area of 0.2 m², what is the pressure in the system? 3 Line Method!!! Formula Enter #’s (with units) Answer (with units)

Example Questions If a man applies a force of 450 N to the input piston of a hydraulic jack which has a surface area of 0.2 m², what is the pressure in the system? P = F A P = 450 N 0.2 m² P = 2250 Pa

Example Questions If there is a pressure of 3000 Pa in a hydraulic cylinder and there is force of 500 N being applied to a piston at the top of the cylinder, what is the area of the piston where the pressure is being applied?

Example Questions If there is a pressure of 3000 Pa in a hydraulic cylinder and there is force of 500 N being applied to a piston at the top of the cylinder, what I the area of the piston where the pressure is being applied? A = F P A = 500 N 3000 pa A = 0.17 m²

Example Questions If we roll a Semi truck onto a hydraulic weigh scale which has 4 m² of pressure plates under it, and the pressure in the fluid below was compressed to a pressure of 3500 Pa, what is the force that weight is applying to the scale?

Example Questions If we a Semi truck onto a hydraulic weigh scale which has 4 m² of pressure plates under it, and the pressure in the fluid below was compressed to a pressure of 3500 Pa, what is the force that weight is applying to the scale? F = P x A F = 3500 Pa x 4 m² F = N

Home Work! You have the remainder of the class to work on this worksheet You will see questions like these on an exam If you need help, come and get it while the get’in is good!! Who has two thumbs and likes stupid smiles… This lady!!!