CHAPTER 11 - FORCE AND PRESSURE
CLASS - 8
FORCE:- Force can be defined as a push or pull on an object.
When more than one Force act on an object in same direction then all forces are added.
As shown in figure, one side of object, Two forces F1 and F2 are applied and both are in same direction on the object then resultant force F3 is sum of both forces F1 and F2 .
. A Force arises due to interaction between two objects.
. Force has both magnitude and direction. SI unit of force is newton, it is represented as 'N' . Changes due to force:-
Change in state of motion :- Force can change the state of the motion and direction. That means the object, which is in rest position, can be moved by applying the force on it and the moving ball can be stopped or changed the direction by applying the force on it.
Change the shape of object :-Force can change the shape of object. Take dough of flour and roll it . After applying some force it turns into Chappati.
. Force may make an object move from rest.
. Force may change the direction of motion of an object.
. Force may make an object rest from move.
. Force may change the speed of moving object.
. May change in the shape of object.
Type of force:- There are two type of force-
1. Contact force 2. Non-Contact force
1. Contact Forces:- Any force that requires contact (touch) to occur, that is known as Contact Force.
Some examples of Contact Force are:-
(A) Muscular Force :- The force is applied on the object by using of muscles of the body, this is known as Muscular Force.
Example:- Lifting a bucket full of water.
(B) Friction :- Friction is the force resisting the relative motion of solid surfaces and fluid layers sliding against each other.
Eample:- Rubbing both palm to each other.
2. Non-Contact Forces:- Any force that does not require contact (touch) to occur, that is known as Non-Contact Forces. Some examples of Contact Force are:-
(B) Electrostatic Force:- The force applied by a charged body on another charged or uncharged body is known as electrostatic force.
Example:- Rub a pen on your dry hair and move above the small pieces of paper. The pieces of papers attract towards the charged pen.
(C) Gravitational Force:- The force which is applied on the object by the Earth due to this the objects or things fall towards the earth, it is known as gravitational force, force of gravity or just gravity.
Pressure:- The force is applied on per unit area of the surface is called pressure.
P = F/A
where P = pressure
F = force
A = area
S.I. unit:-
F = newton (N)
A = meter square (m2)
then SI unit of pressure is ---- P = newton(N)/meter square (m2) or N/m2
Or Pascal (Pa)
Atmospheric Pressure:- The pressure exerted by the air is known as atmospheric pressure.
CLASS - 8
FORCE:- Force can be defined as a push or pull on an object.
When more than one Force act on an object in same direction then all forces are added.
As shown in figure, one side of object, Two forces F1 and F2 are applied and both are in same direction on the object then resultant force F3 is sum of both forces F1 and F2 .
As shown in the given figure , one force F1 act on one side of the object and another force F2 act on opposite direction then the resultant force F3 is equal to difference between the both forces.
. A Force arises due to interaction between two objects. Change in state of motion :- Force can change the state of the motion and direction. That means the object, which is in rest position, can be moved by applying the force on it and the moving ball can be stopped or changed the direction by applying the force on it.
Change the shape of object :-Force can change the shape of object. Take dough of flour and roll it . After applying some force it turns into Chappati.
. Force may make an object move from rest.
. Force may change the direction of motion of an object.
. Force may make an object rest from move.
. Force may change the speed of moving object.
. May change in the shape of object.
Type of force:- There are two type of force-
1. Contact force 2. Non-Contact force
1. Contact Forces:- Any force that requires contact (touch) to occur, that is known as Contact Force.
Some examples of Contact Force are:-
(A) Muscular Force :- The force is applied on the object by using of muscles of the body, this is known as Muscular Force.
Example:- Lifting a bucket full of water.
(B) Friction :- Friction is the force resisting the relative motion of solid surfaces and fluid layers sliding against each other.
Eample:- Rubbing both palm to each other.
2. Non-Contact Forces:- Any force that does not require contact (touch) to occur, that is known as Non-Contact Forces. Some examples of Contact Force are:-
(A) Magnetic Force:- The magnetic force is a consequence of the electromagnetic force, one of the four fundamental forces of nature, and is caused by the motion of charges. The magnet pulls the iron made object without touching.
Example:- Magnet attract the iron pin.
(B) Electrostatic Force:- The force applied by a charged body on another charged or uncharged body is known as electrostatic force.
Example:- Rub a pen on your dry hair and move above the small pieces of paper. The pieces of papers attract towards the charged pen.
(C) Gravitational Force:- The force which is applied on the object by the Earth due to this the objects or things fall towards the earth, it is known as gravitational force, force of gravity or just gravity.
Pressure:- The force is applied on per unit area of the surface is called pressure.
P = F/A
where P = pressure
F = force
A = area
S.I. unit:-
F = newton (N)
A = meter square (m2)
then SI unit of pressure is ---- P = newton(N)/meter square (m2) or N/m2
Or Pascal (Pa)
Atmospheric Pressure:- The pressure exerted by the air is known as atmospheric pressure.
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