Confidential 2020 MEM CLASS VIII PHYSICS CHAPTER 1

CLASS VIII PHYSICS CHAPTER 1 FORCE AND PRESSURE SESSION 8. 1. 4 Confidential ©

TOPICS TO BE COVERED IN THE SESSION: 1. WHAT IS PRESSURE ? 2. HOW

BEFORE WE START OUR SESSION LET’S PERFORM AN ACTIVITY JUST TAKE A BOOK OF

In continuation to what we studied in the last session Pressure The compressive force

In the below mentioned picture you can see that a force of 10 N

In other words, we can say Pressure exerted by liquids and gases Unlike solids,

By this we can say that any pressure applied to a fluid/gas inside a

To summarize: The pressure exerted by water at the deepest point in the ocean

PRACTICE TASK (To be done in notebook) This time we will be doing the

That’s all for today Click on the links given below to learn more about

Slides: 12

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BEFORE WE START OUR SESSION LET’S PERFORM AN ACTIVITY JUST TAKE A BOOK OF MORE THAN 200 PAGES AND HOLD IT IN ONE OF YOUR HANDS (STRAIGHT HIGH UP IN THE AIR) OBSERVE WHAT HAPPENS……. NOW TAKE THE SAME BOOK AND HOLD IT WITH BOTH THE HANDS Did you notice any difference…………. In which of the above two situations your were more comfortable and why ? This makes the basis of our today’s learning----The Concept of Pressure So let’s enter the world of pressure and its effects…………………. . Confidential © 2020, MEM

In continuation to what we studied in the last session Pressure The compressive force acting perpendicular to the surface per unit area is called pressure. Mathematical expression for pressure Confidential © 2020, MEM

In the below mentioned picture you can see that a force of 10 N is applied by a cylinder on a square base whose area is 5 m 2. Here you can see that the cylinder is kept over a square base but we will be considering only that area which is in direct contact with the cylinder. As we know P=F/A, here P=10/5= 2 N/ m 2 or Pascal Now consider the activity you did today(refer to slide no. 4) Fig. 1 You can understand now why it was easy to hold the book by two hands…. . As we know, So as A(area) increases, P(pressure) decreases and vice versa Confidential © 2020, MEM

In other words, we can say Pressure exerted by liquids and gases Unlike solids, liquids and gases do not have definite shape. They take the shape of the containing vessel. So they exert pressure on the walls of the container in which they are kept. Confidential © 2020, MEM

By this we can say that any pressure applied to a fluid/gas inside a closed system will transmit that pressure equally in all directions. (This is also known as Pascal’s Law). As in case of solids pressure was dependent on area, in liquids/gases it increases with depth. To understand this we can perform an activity 1. Take a glass tube or a small piece of transparent pipe and tie a balloon at one end. 2. Hold the tube in vertical position and pour water in it, such that half of the tube is filled with water 3. Observe the bulge produced in the balloon. You will see that the bulge will increase as the height of water increases in the tube. Confidential © 2020, MEM

That’s all for today Click on the links given below to learn more about the topic https: //youtu. be/oz. JC_SM 35 z. Y https: //youtu. be/zl. Lp. Kz. Pz 84 Q STAY HOME…STAY SAFE…STAY HEALTHY SEE YOU ALL SOON Confidential © 2020, MEM