Please can anyone give me the summary of the chapter force and pressure of class 8
Answers
Hello friends.
Class 8 Science Chapter 11 Force and Pressure.
- Force is a push or a pull on an object. Moreover, interaction of one object with another object results in force between the two objects.
hope it's helpful for you...
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The changes that force can bring are written as follows:
moving-fasterChange in speed
If someone pushes your bicycle, it starts moving faster. In this case, the force that we apply on the bicycle changes the speed of the bicycle. Speed can be increased or decreased also.
Note: Force comes into play when at least two bodies interact. Or we can say that two bodies are necessary to put force comes into play.
footballChange in state of body
In this case, the body which is at rest can be put into motion or the body in motion goes in rest. For example: If a football placed on the ground is at rest, when you kick the football, it moves (comes in motion). We can also say that it changes the state of the body.
dimensionChange in dimension
Dimension means shape and size. When you blow a metal rod with a hammer, the dimension changes.
For example: For brushing the teeth, we need to squeeze the toothpaste and apply it on our brush. This leads to a change in the shape of the toothpaste.
driveChange in direction
Force also leads to a change in direction. While playing cricket, the one who throws the ball, throws it in straight position with respect to the one who is doing batting. But the one who is batting hits the cricket ball in different direction.
Another example is that while we drive the car, we push the force on staring due to which car moves or changes the direction.
Top
Types of Forces
There are two types of forces which are as follows:
Contact Force
Non-contact force
Contact Force
contact-forceContact force is the force that acts only when two bodies are in physical contact or two bodies interact with each other.
Examples of contact Force:
Muscular Force
Frictional Force
Mechanical Force
Let us discuss them one by one-
Muscular Force
musclesIt is the force exerted by the muscles. Like when we carry the purse or bag while moving, muscles play a great role. Example: Picking of school bags
Muscular force is the force that is caused by action of muscles inside the body. It is also a contact force. Like we cannot push or pull the book kept on a table without touching it. Or bucket filled with water cannot hold without touch. For this, we need to apply force that will be exerted with hands. This means our muscles play a role.
Animals make use muscular force to carry out physical tasks. Animals like bullocks, horses, donkeys etc need muscular force for different tasks.
Coolies use muscular force to lift luggage.
Athletes use this muscular force for running.
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Frictional Force
It is the force that opposes the motion of one body over the surface of another body. It is a contact force. We can say that in this force, one body tries to move on the surface of another body.
For example, writing anything with pen, book lying on the table, and walking on floor.
machinesMechanical force
It is the force exerted by any kind of machines and obviously it needs contact of another body due to which it is also called as contact force. For example: Turbines in Hydel power station.
Non-Contact Force
It is the force that acts when bodies are not physically in contact with each other. For example: Falling of apple from trees.
Apples always fall down without being in contact with tree and it is due to the gravitational force of earth.
Examples of Non-Contact Force:
Magnetic force
Electrostatic force
Gravitational force
Let us discuss them one by one-
magnetMagnetic force
It is the force exerted by magnets on iron objects.
The force between magnet and iron is attractive type of force, which means it always attract toward each other and never repel each other. It is used in extracting scrap iron from garbage.
electrical-forceElectrostatic force
It is the force of attraction or repulsion exerted between charged particles.
It can be either between same charges (repulsive, this means they repel each other) or between opposite charges (attractive, this means that they both attract each other).
gravitational-forceGravitational force
It is the force exerted by earth’s gravity on all objects. It is always attractive in nature.
For example: Falling of apple from tree or falling of any object when we through anything up.
Hope it helps...
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