Definition Of Work

Definition Of Work


"Work is said to be done when an object moves (displaces) along the direction of application of force."
OR The work is defined as force � displacement.
W = F x S 

More About Work:

In order to do the work two conditions are required to be fulfilled.
Force must be applied 
Object must displace certain distance
Even after applying the force on an object if the object does not moves then the work done is zero.
Force is the cause of the motion. Without using the force, objects will not displace themselves due to Inertia (tendency of a body to continue in its state).
The mechanical energy used while applying a force is called work.
S.I unit of work done is joule.
W = F X S = (Force is measured in Newtons and the displacement in meters). Hence the work done = Newton X meter = 1 Joule. 

Example 1: A child pushes the chair forward and the chair will fall backward (not properly balanced). Now the work done by the child is zero, because the chair is not moving forward. 
In order to do the work Body/Object must displace along the direction of force
Example 2: Three persons were working on a railway track, and like to move the iron rod through a distance of 1 meter. 400 N of force is applied by the three persons but the rod is not getting displaced. What was the work done by the three people?
Answer: Zero

Reason: As there is no displacement (iron rod has not moved). Force X zero = 0 

Examples of Work

A magnet attracting an iron nail.
The spring in pulling a weight.

Solved Example on Work

A force 30N is applied on w body and the body moved a distance.10 m, then the work done is

A. 30J
B. 30J
C. 300J
D. 0.3J
Correct answer is C. 

Solution :

Step 1: Write down the equation of work. W = f.dx 
Step 2: Step 2: Insert the value of the force and displacement, in Newton and distance in meters =30�10 
Step 3: Write down the final answer in joules.
Step 4: W = 300j