just a general doubt....

This is a very good doubt..

See the work done by gravity is -ve of grav potential energy

So if you see closely,

net work done on the body = net change in the kinetic energy of the body

work done on the body by gravitaion + by other forces = net change in the kinetic energy of the body

Thus,

-ve of gravitational potential energy + by other forces = net change in the kinetic energy of the body

Thus work by all forces other than gravitation = net change in kinetic + potential energy...

For a even better understanding try to understand the derivation of work energy theorem (it is a one line derivation :)

ok...

I will give the derivation of work energy theorem

F.ds = dW

For all the external forces,

\sum{F_i} = m.a

Thus,
\sum{F_i} = m.\frac{dv}{dt}

\sum{F_i.ds} = m.\frac{dv}{dt}.ds

\sum{F_i.ds} = m.\frac{ds}{dt}.dv

\sum{F_i.ds} = m.v.dv

Integrating on both sides

\int \sum{F_i.ds} = \int m.v.dv

\sum{\int F_i.ds} = \int m.v.dv

\int F_i.ds is the work by each individual force

\int m.v.dv = 1/2m(v_f^2-v_i^2)

now see the LHS has mg as force... so the potential energy is taken care by the work done by graviation on the LHS..

That is why we only consider kinetic energy..

Yes shreya.. You have put it correctly :)