Physics "pressure" class 7

This presentation if for grade 7
and it is for the chapter: 13 from Oxford physics for u

1. Pressure 25/9/2018 Grade 7 CHP: 13 Physics

2. Force and pressure

3. Force and Pressure are NOT the same thing • Force: is the total impact of one object on another. • Pressure: is the amount of force acting on an area. Force and pressure

4. • Describes how a force is spread over an area • It is a measure of how much force is acting on a certain area. Pressure

5. Pressure Pressure = Force / Area Newton per metre squared = Newton / metre squared N/m2 = N/m2 Another equivalent unit is used for N/m2, Pascal (Pa)

6. Pressure Pressure depends on 2 factors: • Forces acting – Increasing the force will increase the Pressure. • Area of surface – Decreasing the area of the force will increase the Pressure.

7. Pressure in Liquids

8. Pressure in Liquids • Pressure is transmitted throughout the liquid. •Pressure acts in all direction. • Pressure increases with depth.

9. Pressure increases with depth

10. Pressure in Liquid Formula

11. Hydraulic Machines

12. Things to remember : • Pressure in a liquid is transmitted equally and throughout the liquid.

13. Atmospheric Pressure or Gas Pressure

14. Air pressure Air has mass. Therefore air has weight. Air has particles that are continually moving and colliding with things on Earth. These collisions produce air pressure. Air presses down all things in the Earth’s surface. The pressure exerted by air is known as A ir pressure or Atmospheric pressure. The features of Air pressure are: a) acts in all directions b) changes from one place to another c) decreases the higher you go above the ground level. This feature exists because at high place, the amount of air decreases. This explains why the air pressure on the top of a mountain is lower than at the foot of the mountain.

15. Gas pressure increases when:

16. Drinking straw

17. Measuring Instrument

18. Mercury Barometer • Atmospheric pressure can be measured with a mercury barometer . • The column of mercury is held up by air pressure. • As the air pressure varies from day to day the height of the mercury also varies

19. Manometer

20. Done by: Abdul Rahman Moez Grade: 7