Work is said to be done by a force on a body, if the body moves in
any direction except at 90^{0} from force.

It is defines as the scalar product of force vector and displacement vector.
i.e.
W = FScos
Where
is anbgle between

It is scalar quantity. It's SI unit is
Joule (Kgm
^{2}s^{-2}) and cgs unit is (gcm
^{2}s^{-2}). It's dimensional formula is [ML
^{2}T^{-2}]

If
is anbgle between
< 90^{0} then work done will be positive

i.e. w = Fscos
= positive works

For eg: When oject is falling freely under the action of gravity than work done by gravitational force an the
object is an example of positive work.

If
= 90^{0} then work done wil
be zero

i.e. w = Fscos90^{0} w = zero work

For eg: When a man carrying a load on his head and moving on a horizontalroad then work done by man on the load
is an example of zero workdone.

If
< 90^{0} 180^{0} then work
done wil be negative

i.e. w = Fscos180^{0} w = Negative work

For eg: When object is thrown verticaly upward against the gravity then workdone by gravitational force on
the object is an example of negative work.

Energy:

The capacity of doing work is called energy. It is scalar quantity and its unit in SI syste is joule and cgs is
erg. Dimensional formula is [ML
^{2}T^{-2}] 1 J = 10^{7} erg.

Various Forms Of Energy are:

Heat Energy

Light Energy

Electrical Energy

Mechanical Energy(Kinetic Energy + Potential Energy)

Kinetic Energy:

The energy possess by an object due to it's motion is called
Kinetic Energy. Expression For K.E.

Consider an object mass "m " is initially at rest. Suppose
a constant force 'F' is applied on object to produce a displacement
Now, work
done by constant force, W =
.
W =
Fscosϴ (Where ϴ is angle between F and S vector) W = Fscos0 W = Fs W = mas ..........i)

F = ma
where a is the acceleration of object. If v be the final speed attained by an object then from equation of motion
v^{2} = u^{2} + 2as we ca write: v
^{2} = 0^{2} + 2as (since u=0) v
^{2} = 2as v
^{2} / 2 = as ..........ii)

From eqn i) and ii), we get,
w = m × v^{2} / s w = 1/2 mv^{2}

This work done is equal to kinetic energy
Kinetic energy = 1/2 mv^{2} .........iii)

Work Energy Theorem

The total work done by a force acting on a body is equal to total change in
it's kinetic energy. i.e, Total workdone = Total change in knetic energy

Proof:,

Consider an object mass 'm' is moving with constant speed 'u'. Suppose a constant force F vector is
applied on object is produce a displacement S vector. Now, workdone by constant force W =
.
W =
Fscosϴ (Where ϴ is angle between F and S vector) W = Fscos0 W = Fs W = mas .......i) (since f =
ma where
'a' is acceleration of a object)

If v be the final speed attained by an object then from equation of motion v
^{2} = u^{2} + 2as Now from eqn i) and ii)

W = 1/2 mv^{2} - 1/2
mu^{2}

Total work done = final K.E - Initial K.E Therefore, Total work done = Total change in
kinetic energy which is work energy theorem.

Potential energy:

The energy possesses by an object due to its position or configuration is
called potential energy.

Gravitational Potential Energy = mgh Elastic Potential Energy = 1/2
kx^{2}

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qustions section!!!!