Page 367 - Class 8th Force notes
➤Force - Force is that factor which, being applied to an object, brings about a change in its state or tries to bring about a change.
Force is denoted by "F".
The SI unit of force is the newton. Which is denoted by "N".
Its CGS unit is Dyne.
The F.P.S. unit of force is Poundal.
Note:-
1Newton = 100000 Dyne
1Newton = 0.10197 kg
1kg = 9.81Newton
1Newton = 7.23301 Poundal
(force formula)
F = ma
where ,
F = Force ➡ in Newton
m = mass ➡in kg
a = acceleration ➡in m/sec^2
➤ Effects of force :-
Force has three effects:
1. it can change the speed of the object, which can cause the object to become stationary or to slow down.
2. The direction of motion of the object can change.
For example, when a ball is dropped from above on the ground, the ball bounces upwards. 3. 3. The size of the object may change.
Fore example , when the ball is pressed with the palm, it gets pitched.
➤What is pressure?
The force acting per unit area is called pressure.
Pressure = Force /Area
➤What is called Thrust ?
The vertical force acting on the entire surface area of an object is called thrust or arc.
Thrust = Area x Pressure
➤What is the atmosphere called?
The envelope of air that surrounds the surface of the earth is called the atmosphere.
➤What is air pressure?
The pressure exerted by the atmosphere on a unit area of the surface of an object is called air pressure.
➤What is vacuum?
A place where there is nothing even if there is no air, it is called vacuum.
➤What is atmospheric pressure?
The pressure of air that balances a column of mercury 76 cm high is called atmospheric pressure.
Note :- Atmospheric pressure is expressed by "atm".
1. Contact force:- Contact force - The force which is applied when an object comes in contact is called contact force. For example (i) Frictional force between the pages of a book and a table. (ii) Muscular force applied when muscles are in contact with an object.
Force is denoted by "F".
The SI unit of force is the newton. Which is denoted by "N".
Its CGS unit is Dyne.
The F.P.S. unit of force is Poundal.
Note:-
1Newton = 100000 Dyne
1Newton = 0.10197 kg
1kg = 9.81Newton
1Newton = 7.23301 Poundal
(force formula)
F = ma
where ,
F = Force ➡ in Newton
m = mass ➡in kg
a = acceleration ➡in m/sec^2
➤ Effects of force :-
Force has three effects:
1. it can change the speed of the object, which can cause the object to become stationary or to slow down.
2. The direction of motion of the object can change.
For example, when a ball is dropped from above on the ground, the ball bounces upwards. 3. 3. The size of the object may change.
Fore example , when the ball is pressed with the palm, it gets pitched.
➤What is pressure?
The force acting per unit area is called pressure.
Pressure = Force /Area
➤What is called Thrust ?
The vertical force acting on the entire surface area of an object is called thrust or arc.
Thrust = Area x Pressure
➤What is the atmosphere called?
The envelope of air that surrounds the surface of the earth is called the atmosphere.
➤What is air pressure?
The pressure exerted by the atmosphere on a unit area of the surface of an object is called air pressure.
➤What is vacuum?
A place where there is nothing even if there is no air, it is called vacuum.
➤What is atmospheric pressure?
The pressure of air that balances a column of mercury 76 cm high is called atmospheric pressure.
Note :- Atmospheric pressure is expressed by "atm".
There are the following types of forces:
1. Contact force
2. Non-contact force
3. Balanced force
4. Unbalanced force
5. Centripetal force
6. Gravitational force
7. Magnetic force
8. Electric force
9. Muscular force
10. Frictional force
1. Contact force:- Contact force - The force which is applied when an object comes in contact is called contact force. For example (i) Frictional force between the pages of a book and a table. (ii) Muscular force applied when muscles are in contact with an object.
2. Non-contact force:- Non-contact force is the force which is applied without coming in contact with an object. Some examples of non-contact forces are - gravitational force, electrostatic force, magnetic force.
3. Balanced force:- When the sum of all forces applied on an object is zero, then those forces are called balanced forces. Balanced forces do not change the static state or motion of an object.
4. Unbalanced force:- When the resultant force of the forces acting on an object is not zero, then it is called unbalanced force. The position of the object changes due to unbalanced force.
5. Centripetal force:- When an object moves on a circular path, then a force acts on it at the center of the circle, this force is called centripetal force. In the absence of this force, the object cannot move on a circular path.
6. Gravitational force:- The mutual attraction acting between particles is called gravity and the force produced by it is called the force of gravity.
7. Magnetic force:- The force acting between two magnetic poles or a magnetic pole and a magnetic substance is called magnetic force. This force is of attraction or repulsion. Magnetic force is produced due to the motion between electrically charged particles. 8. Electric force:- The force of attraction or repulsion between any two charged objects is called electric force. This force is one of the four fundamental forces of nature. Electric force is responsible for many phenomena ranging from attraction and repulsion of charged particles to conduction of electricity in substances.
9. Muscular force:- The force applied by the muscles of the body on an object is called muscular force. It is a contact force. Muscular force is produced due to expansion and contraction of muscles.
10. Frictional force:- Frictional force is the force that opposes the motion between two objects. This force is applied on the surface of contact when the objects come in contact. The frictional force is applied in the opposite direction of the motion of the object.
The End
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कृप्या इस लेख को अधिक - से - अधिक शेयर करदें ।
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