Connecting Bodies(Laws of Motion)
In mechanics we come across many types of forces like gravitational force, contact force, tension in string, spring force etc.
1.Gravitational force: It is force between any two mass particles.
Every body in the universe experiences gravitational force. Also it governs the motion of celestial bodies
2. Contact forces: This force arises due to contact of an object with some solid or fluid
a)Contact force due to contact of a solid with solids.
Eg: If a book is placed on a table, a pair of forces satisfying Newton's III law arise due to contact between the table and book.
If some force tending to move is applied on the above book the contact force acts at some angle to the surface of table. The component of contact force normal to surfaces in contact is called normal force and the component of force parallel to surface is called friction.
b) Contact force due to contact of a solid with fluids.
Eg: Viscous force, air resistance