Work energy theorem is valid-

The correct answer is option 4) i.e. for all type of forces

CONCEPT:

• Work-energy theorem: The work-energy theorem states that the net work done by all the forces on an object equals the change in its kinetic energy.

​Work done, 

Where m is the mass of the object, v is the final velocity of the object and u is the initial velocity of the object. 

EXPLANATION:

• Energy and work are scalar quantities.
  • So, their values depend on the sum of individual work done by the forces. If these forces cause a displacement, it will be accounted for in work done.
• The work-energy theorem can be applied in the cases of conservative forces, non-conservative forces, internal forces, external forces, and so on.
• Thus, the work-energy theorem is valid for all types of forces.