1. Topic 4: Pressure

2. Pressure = Force÷Area p = F/A The unit for pressure is the pascal, which is written as Pa. 1 Pascal = 1 Newton/1 square meter Pa = N/m 2 Eg. A woman has a weight of 600 N, and the soles of her feet have a combined area of 0.5 m 2, what is the pressure on her feet? p = F/A = 600N/0.5m 2 = 1200 Pa.

3. Pascal’s Law In a closed system, where the fluid cannot escape, any pressure that is placed on the fluid will be transmitted equally in all directions. Pascal’s law is used in hydraulic systems like car lifts. Hydraulic systems involve a large mechanical advantage.

4. Hydraulic Systems Hydraulic systems involve a small cylinder which pressurizes the liquid. Pascal’s law says that the pressure will travel, undiminished, throughout the liquid. In a hydraulic system the pressure will cause the cylinder at the other end to raise up.

5. Pascal’s Law and Hydraulics According to Pascal’s law, the pressure is the same on both ends, therefore the force at the larger cylinder (larger area) will be larger than the effort force going onto the smaller cylinder. pressure in = pressure out →F in /A in = F out /A out

6. Example A mechanic exerts a force of 200 N on a 0.5 m 2 piston cylinder. At the other the large, 10 m 2 cylinder moves up. What is the most force that it can exert upward? p input = F input /A input = 200 N/0.5 m 2 = 400 Pa p input = p output = 400 Pa F output = 400 Pa X 10 m 2 = 4000 N