You must have seen the stickers of push and pull on doors at different places. By pushing or pulling we make the door to move either in a backward or in a forward direction. So push and pull is nothing but a force and this force changes the state of motion of an object in a particular direction. In NCERT Solutions for Class 8 Science Chapter 11 Forces and Pressure, you will study about the different types of forces and pressure which you apply in your daily life.
Force is either a push or a pull on an object resulting from interaction with another object.
Few examples of force are listed below
Example 1: A man pushing a car is an example of interacting force: when a man pushes a car there is an interaction between man, car, and ground. While pushing a car we not only push car with hand, but also we apply force to ground through our leg.
Example 2: while pulling or pushing a door there is an interaction between our hand and door. This interaction results in motion of the door.
Force can change the direction of motion of an object.
Example 3: when we pass a ball the direction of ball changes.
In the above figure, the ball has been passed between two people and finally to the post. Here the direction of the ball is changed by applying a force on the ball by the hand. Such examples are given in NCERT Solutions for Class 8 Science Chapter 11 Forces and Pressure
Force can change the shape of an object:
Example 4: If we stretch a rubber band the shape changes
In the above figure rubber is attached to a cube and the shape of rubber is that of a square.
Force can be attractive or repulsive.
Example: if we brought two magnets it will either stick together(attraction) or it will oppose each other(repulsion)
Force can change the state of motion
Example 5: A moving ball can be stopped with our hand. That is we are changing the state of motion to rest.
Example 6: A ball moving in ground stops itself after some time. That means something is opposing the motion of the ball. This opposing thing is also a force called friction.
In the above figure, friction is opposing the motion of the ball and finally the ball stops
Another concept of the chapter 11 Force and Pressure is a muscular force: while lifting a bucket of water we are applying a force against the weight of bucket with our muscle. This force applied by our muscle is known as muscular force
In the above figure, the bucket is not moving since muscular fore balances the weight of the bucket. Such many interesting examples are presented by NCERT Solutions for Class 8 Science Chapter 11 Forces and Pressure.
Here is the Paheli's question:
The second important topic which you will study in this chapter is pressure.
For example Gas or liquid inside a container exerts force on walls of the container. This force per unit area of the container is called pressure. When we put a hole in the container gas or liquid leaks out. This indicates liquids or gases are exerting pressure on walls of the container. This example is also given in NCERT grade 8 chapter11 This is depicted by the below figure.
Another topic introduced by NCERT grade 8 Science Chapter 11 Forces and Pressure is atmospheric pressure. The pressure exerted by air around us is known as atmospheric pressure. The value of atmospheric pressure is very large, but our body is not experiencing it because the pressure inside our bodies is also equal to the atmospheric pressure and balances the pressure from outside
The main topics of NCERT Class 8 Science Chapter 11 that is forces and pressure are listed below:
11.1. Force – A Push or Pull
11.2. Forces are due to an Interaction
11.3. Exploring Forces
11.4. A Force can Change the State of Motion
11.5. Force can Change the Shape of an Object
11.6. Contact Forces
11.7. Non-contact Forces
11.9. Pressure Exerted by Liquids and Gases
11.10. Atmospheric Pressure
There are so many interesting examples and situations that are given in the NCERT book grade eight-chapter 11. You can do all the activities given in the NCERT book and it will be a fun and learning experience.
At the end of the chapter force and pressure, you have to solve all the given questions. This will be interesting and you can experience what you are studying. In case if you have any doubt then you can find the answers at NCERT Solutions for Class 8 Science Chapter 11 Forces and Pressure, this will help you to understand the concept and score more marks.
When we press the bulb of a dropper with its nozzle kept in water, the air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to
(a) pressure of water.
(b) the gravity of the earth.
(c) the shape of a rubber bulb.
(d) atmospheric pressure.
The rise of water in the dropper is due to atmospheric pressure. The atmospheric pressure is more than the pressure inside the dropper thus pushing the water inside it.
You can view the complete NCERT Solutions for Class 8 Science Chapter 11 Forces and Pressure in detail and with necessary figures below.
Q1. Give two examples each of situations in which you push or pull to change the state of motion of objects.
Q10. When we press the bulb of a dropper with its nozzle kept in water, air in the dropper is seen to escape in the form of bubbles. Once we release the pressure on the bulb, water gets filled in the dropper. The rise of water in the dropper is due to
(a) pressure of water.
(b) gravity of the earth.
(c) shape of rubber bulb.
(d) atmospheric pressure.
Q7. An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?