Type Of Forces In Physics | Contact Force | Frictional Force
Type of Forces
There are three forces which are commonly used in mechanics-
Field forces- These are the forces in which contact between two bodies is not necessary. The gravitational force between two bodies and the electric force between two charges are two examples of field forces. weight force also is a field force.
Contact force- Two bodies are in contact with exerting equal and opposite forces on each other. If the contact is frictionless the contact force is perpendicular to the common surface and known as a normal reaction force.
If however the object is in rough contact and moves relative to each other without losing contact then frictional force arises which oppose such type of motion again each object exert equal in magnitude and opposite in direction frictional force.
Suppose frictional force and normal reaction both are acting on a body then the contact force is the resultant of both frictional force and normal reaction.
\(\left( F\right) _{cont}=\sqrt {N^{2}+f^{2}}\)
Example- Consider two wooden blocks X and Y being rubbed against each other ‘X’ is being moved to the right 
while ‘Y’ is being moved leftward. In order to see more clearly which forces act on ‘X’ and which on ‘Y’, a second diagram is drawn, so space between the block but they are still supposed to be in contact.
The two normal reactions each of magnitude equal and are perpendicular to the surface of conduct between the block, and the two frictional force each of magnitude f acting along the surface is in a direction opposite to the motion of the block upon which it acts.
