3. General idea:  The column of air exerts a force on the surface of the earth.  This force per area is as large as 1.03x10 5 Pa at sea level, also known as the atmospheric pressure.  Approximately the same pressure that an elephant bull weighing (7000 kg) approx. 70.0kN exerts on a 1.5 square meters of area.

6.  It is not safe to dive at a great depth under water because you will be crushed by the weight of water above you.  That’s why the material for the construction of submarines has to be secured thick and strong or else it would be crushed like a tin can under your feet.

7. Pressure  Basic: the amount of force per unit of area. A B c

8. Which exerts greater pressure on the surface? B A C

9. B A C

10. B A C

11. Gauge vs. Absolute Pressure  Absolute Pressure  Zero referenced to a perfect vacuum.  Gauge Pressure  Zero referenced to ambient pressure

12. Where is there greatest pressure? A B C D

13. Pascal’s Principle on Hydrostatic pressure  Pressure exerted on a  confined fluid is  transmitted undiminished to  all parts of the fluid and  walls of its container  Also called as Pascal’s Law or  Pascal’s Principle of Transmission of Fluid Pressure

14. Where is there greatest pressure? A B C D

15. Other applications of Pascal’s Law  Hydraulic lift

16. Which exerts greater pressure on the surface? ABC ALCOHOLWATERMERCURY

17. What is the total pressure at the bottom? C MERCURY A B WATER ALCOHOL

18. Lecture Point  Find the gauge and absolute pressure on the points indicated.  (Illustration is given on the board)

19. Exercises  What downward force exerted on a small piston of radius 2.00 cm would lift a 2.00 x 10 3 kg car, if the radius of the large piston is 12.0 cm?

20. Exercises  The maximum gauge pressure that the components of a hydraulic lift can withstand is 15 times the normal atmospheric pressure. If the diameter of its output piston is 32.0 cm what is the maximum mass it can lift?