# CBSE Class 8 Science Revision Notes Chapter 11

## CBSE Class 8 Science Revision Notes Chapter 11 – Force and Pressure

Class 8 Science discussed force and pressure in Chapter 11, including the definition of force and its various types. Through this chapter, students will understand how force is generated with appropriate examples. To learn the fundamental concepts of this chapter, students can access the chapter Force and Pressure Class 8 Revision Notes. These notes simplify the new concepts and concentrate on increasing students’ knowledge base.

By referring to Extramarks Revision Notes, students can easily cover the chapter’s content since it is written in easy-to-understand language and a concise format. These brief and comprehensive notes are ideal for a quick review of the chapter as well as in-depth revision sessions. These notes are reliable since they are carefully prepared and reviewed by subject matter experts referring to the updated CBSE syllabus. The material is easily accessible from the Extramarks website.

## Revision Notes for CBSE Class 8 Science Chapter 11

### Access Class 8 Science Chapter 11 – Force and Pressure

Definition of Force:

A push or pull that modifies or tends to modify an object’s resting or uniform motion state is referred to as force.

It may change the direction or shape of the object.

Example: simple actions involving force, which include opening a pencil box/lunch box, kicking a football, lifting a box, pushing a chair, and so on.

In each of these cases, a push or pull is applied to the object in order to change its state of motion. The football continues to kick as if the closed pencil box is being opened.

The SI unit system uses Newton as the unit of force.

Effects of Force:

1. The interaction between two objects produces a force. For example, a football needs to be kicked to move. The football moves as a result of the force produced by the interaction between the person and the football.
2. A force has strength, which is measured in magnitude and direction. The magnitude of the applied force can be large, small, or equal. The forces can be applied in the same or opposite directions. These modify the force’s effect on the object. Two people pushing a heavy object in the same direction is easier than two people pushing it in opposite directions to move it.
3. An object’s speed, direction of motion, or both can be affected by a force. This shows a change in the object’s state of motion. When a player kicks a football, the ball moves in the same direction. The object’s speed is determined by the amount of force being applied to it.
4. A force acting on an object has the potential to change its shape. By applying force and rolling, the dough can be formed into chapatis.
5. A force can exert an effect on an object by coming into contact with it or not coming into contact with it.

Types of Force:

There are two kinds of force depending on whether the force acting on the item is in contact with it. Depending on the sort of touch or non-contact force being used, each of them can be further categorised.

1. Contact Force: An object experiences a contact force when it comes into contact with the body. The point of application of force or the point of contact is the location where force is applied to an object.

The contact forces are classified as follows:

• Muscular Force: A muscular force is a force that is exerted as a result of the action of the muscles in bodies. Some of the bodily functions, such as breathing and digestion, rely on muscular force. Animals such as buffalo, camels, and horses use their muscular force to perform tasks for us such as ploughing, pulling, and carrying a load.
• Frictional Force: A frictional force is one that opposes an object’s motion and always acts in the opposite direction of the object’s motion. A boat stops moving when there is no rowing. The frictional force between the boat and the water is the reason.
1. Non-Contact Force: A non-contact force is one that does not involve any physical contact between the two objects on which it acts.

Non-contact force is classified as follows:

• Magnetic Force: it is defined as the force exerted by a magnet on objects made of iron, steel, cobalt, or nickel without coming into contact with them.
• Electrostatic Force: An electrostatic force is a force exerted by a charged body on another charged or uncharged body. It may result in the attraction of opposite charges if we bring a charged straw near an uncharged straw and the repulsion of similar charges, if we bring two straws, rubbed with paper charged near each other.
• Gravitational Force: A gravitational force is an attractive force that every object in the world exerts on another object.

Pressure:

1. The unit force acting on a surface per unit area is called pressure. The following is a definition of the pressure-force relationship:

Pressure = ForceArea on which it acts

Pressure is defined as the product of a force and the surface area on which it acts.

1. Because the smaller surface puts more pressure for the same amount of effort and the nail enters the wood with a single push, it is easier to drive a nail into a wooden board with a pointed end than the head.
2. The SI system uses Newton per square metre, or 1 Pascal, as the unit of pressure measurement (Pa).
3. It is clear that gases and liquids can exert pressure much like solids.
4. A solid typically only applies downward pressure because of its weight.
5. Liquids and gases, on the other hand, exert pressure in all directions. It should be noted that when a water pipe leaks, fountains of water appear in all directions. This is due to the water exerting pressure on the pipe walls. Similarly, when there are holes in a balloon, air escapes in all directions. As a result, the liquids and gases exert pressure on the container’s walls.

Atmosphere:

1. The thick layer of air that covers the earth above its surface is known as the atmosphere.
2. This column of air in the atmosphere exerts pressure, which is known as atmospheric pressure. A rubber sucker remains fixed to the surface because of this pressure.
3. The enormous atmospheric pressure that surrounds us is invisible. This is because our body’s internal fluid pressure actually balances the pressure of the air around us.

### Force and Pressure: Class 8 Science Chapter 11 Revision Notes Summary

The concepts of force will be introduced in this chapter. Previously, students have learnt the various types of forces. In this chapter, they will understand the definition of force and how it is classified.

The introductory section will explain how force is measured and the unit is determined. It is important for students to understand these fundamental concepts as they are further discussed in higher classes. They can find simple Class 8 Science Chapter 11 revision notes on the definition and explanation of force at Extramarks.

A description and differentiation of push and pull forces follow in Science Class 8 Chapter 11 notes. These concepts are described with appropriate illustrations to help students remember the concept. Then, they will learn about magnetic force. This force is an excellent example of a non-contact force, as it cannot be seen or felt, but its effect can be observed. The section discusses magnetic force in terms of attraction, repulsion, and rotation caused by the two magnetic poles.

The various classifications of force will be covered next. It is divided into two categories: push and pull. Students will learn about friction force, gravity, magnetic force, applied force, buoyancy, tension, drag force, spring force, and other forces in this chapter. On a more advanced concept level, the chapter will also explain how to calculate the net force operating on a body. The idea of the net force, also known as the resultant force, will be introduced. To understand the meaning of resultant or net force, students can consult Force and Pressure Class 8 Notes.

The idea of the state of motion is introduced in the following section. Speed and velocity will be defined and described. The Force and Pressure Class 8 notes contain relevant descriptions and examples that will expose students to the many sorts of forces. Following this, thrust and pressure will be explained. Understanding the definition of thrust will be simple once students understand what force is. This section will teach them to calculate pressure, with interesting facts and concepts.

The later part of the book will demonstrate how pressure is distributed in a liquid and transmitted to all parts of a container. This section will also explain how the same force applied to a smaller area produces more pressure and vice versa.

In the chapter, each new concept will be discussed with appropriate examples and illustrations. Students will then learn about buoyancy, which is the physical phenomenon that determines whether or not a body will float in a liquid. Extramarks Science Class 8 Chapter 11 Notes provide a concise explanation of these concepts.