What is Force?

Force :- Push or pull that affects an object in some way is called a force.
• Force is measurable quantity.
• SI unit of the magnitude of force is Newton (N).
• Force has both magnitude and direction.
[Vector quantity].

EFFECT OF FORCE :-
(i) Force can make a stationary object move.
(ii)  Force can stop a moving object.
(iii) Force can change the speed of a moving object.
(iv) Force can change the direction of moving object.
(v) Force can change the shape of an object.

THERE ARE TWO TYPES OF FORCE :-
(1) Contact force.
(2) Non-contact force.

1. Contact force - Force which require physical contact is known as contact force.
*There are three types of contact force :-
(i) Muscular force
(ii) Mechanical force
(iii) Frictional force

Muscular force - A force that requires that action of Muscles of our body is called muscular force.

Mechanical force - The force generate by a machine (for example the engine of a car) is called mechanical force.

Frictional force - [oppose relative motion]
Force that opposes motion whom two surfaces in contact move or tend to move with respect to each other is called Frictional force.
-  The direction of this force is opposite to the direction of motion.
- It has internal force
- It always generate in pair.

2. Non-contact force - Force that arise due to interaction between objects that are not in physical contact are called Non-contact force.
- Also known as distance force.
- Non-contact forces act From a distance.

* There are three types of Non-contact force:-
(i) Gravitational force
(ii) Magnetic force
(iii) Electrostatic force

Gravitational force - Every object is pulling every other object towards itself. This force of attraction called gravitational force.
- Force acts between two bodies.
- Always attractive.
- Internal force.
- Central force.

• Gravitational force = Gm1m2/r2

Magnetic force - Magnetic force is a force that attracts certain metal objects (like iron and iron fillings) towards a magnet is called magnetic force.
- Magnetic force can be both attractive and repulsive.
• Like pole repel each other.
• Unlike pole attract each other.

Electrostatic force - Force between the  two charged bodies exert a force on other changed or uncharged bodies is called electrostatic force.
- This force deos not require physical contact between the two bodies.
- Non-contact force.
- Central force.
- Electrostatic force could be both attractive and repulsive.

• Two charged bodies repel ech other.
• Two uncharged bodies attract each other.

There are two types of charge:-
(i) Positive charge (+).
(ii) Negative charge ( - ).

BALANCE FORCE :-
Two or more forces acting on an object are said to be balanced forces, if the net affect produced by all the object is zero (0).
- The balanced forces do not change the state of the body.

UNBALANCED FORCE :-
If the net affect produced by two or more forces on an object is not zero, then the forces are said to be unbalanced forces.
- The unbalanced forces change the state of the body.