Force

Force 

A push or pull which when acts on a rigid body produces motion in the body which is initially at rest or stops the body moving in a uniform motion is called force

In the figure shown below both the cases of push and pull are explained

Unit of force :

The SI unit of force is 'Newton'. 

According to Newton's second law of motion force is the product of mass and acceleration. The SI unit of force can be derived from this expression as follows

Some other conversions of this unit to another unit are shown below 

These units are considered as absolute unit of force.

Characteristics of a Force :

Characteristics of a force means the properties of a force that define it completely.

For example:

Consider a rigid body acted upon by a force of 10 Newton at a point O. Following are the characteristics of that force:-

• Magnitude 

The quantity of force applied to a rigid body is called magnitude i.e. 10 Newton.

•  Direction 

Direction is the the line of action of force or it can be defined as the the direction in which force is assumed to be acted upon.

• Sense

Sense is the nature of force acting on a rigid body, It can be a push or pull indicated by an arrow towards the rigid body or away from the rigid body as shown in the fig below.

• Point of Application 

It can be defined as the point where force is assumed to be acting. for a point load the point of application of force is just below the force whereas for uniformly distributed load the point of application of force lies in the the middle of the force.

  Representation of a force:

A force which is a vector quantity which has both magnitude as well as direction and it can be represented as follows

Consider a force of 5 Newton acting on a rigid body.

The length of the arrow shows the magnitude of force that is 5 cm = 5 Newton and the direction of Arrow represents the direction of force.

If the force is acting at an angle θ from the x axis it can be said that the direction of force from the x axis is θ degree.