LEARNING OUTCOME • Introduction To Work • Need of Force For Work • Mathematical Expression For Work • Unit of Work • Definition of Joule • Zero Work And Its Examples

1. Work ,Energy and Power
PART -1
FUNDAMENTALS OF WORK
AND ZERO WORK

2. Work
Work is mode of transfer of energy i.e., without
transter of energy there is no meaning of physical
work.
Any activity that requires muscular or mental effort
like pull a heavy sofa across a room, lift a stack of
books from floor to a high shelf, to prepare a lesson
in two hours.

3. Work transfers energy with the
help of force.
For example, when a weight lifter
lifts weight, he applies force and
displaces the weight.
Then we say that work has been
done by the weight lifter.

4. When Constant Force is Acting in
the Direction of Displacement

5. If a horizontal force F is applied on the body, kept
on a smooth horizontal surface.
This force acts on the body for some time during
which the body displaces by ‘s’.
So the work done by a force on a body is the
product of force and displacement of the body.

6. Work= Force x Displacement
W = F x s
Work is a scalar quantity. This means that it
has no sense of direction.

7. Unit of Work
The S. I. unit of work is joule.
The C.G.S. unit of work is erg.
1J = 107 erg

8. Definition of Joule
When F = 1N, s = 1m, then W = 1J
One joule of work is said to be done when a
force of one Newton (N) displaces a body by
one metre (m) in its own direction.
1J = 1N x 1m

9. Zero Work
If s = 0, then W = 0, i.e., work done by
a force on a body is zero if the
displacement of the body is zero.
For example, when we push a wall
with a force F, then the displacement
of the wall is zero. Therefore, the
work done by force F on the wall is
zero.

10. 2. If we sit on a chair and
prepare a lesson in two
hours. Then we may feel
tired.
But according to definition,
no work is done, becuase
there is no displacement.

11. 3. If we hold a briefcase for
one hour and do not move the
briefcase.
Then displacement (s) of the
briefcase is zero.
Therefore, work done on the
briefcase is zero.
S=0

12. Thank You