Physics XI Content
WORK
|
|||
PHYSICAL DEFINITION OF WORK
|
|||
“Work is said to be done if a force causes a displacement
in a body in the direction of force”. OR “The work done by a constant force is defined as the product of the component of the force and the displacement in the direction of displacement.” |
|||
MATHEMATICAL DEFINITION
|
|||
“Work is the scalar product of force and displacement”. OR
“Work is the dot product of force and displacement”. |
|||
UNIT OF WORKS
|
|||
• In S.I system: Joule (j) • In C.G.S. system: Erg • In F.P.S. system: ft X lb |
|||
CATEGORIES
OF WORK |
|||
(i) POSITIVE WORK: | |||
If force and displacement are in the same direction, work will be positive or if q = 0 orq< 90° | |||
(ii) ZERO WORK: | |||
If force and displacement are perpendicular to each other, work will be zero. i.e. | |||
since q = 90°
Work = 0 as Work = Fd Cos q Work = Fd Cos 90° Work = (F)(d)(0) Work = 0 |
|||
NEGATIVE WORK: | |||
In force and displacement are in the opposite direction, work will be negative. | |||
Since q = 180°
Work = – ve as Work = Fd Cos q Work = Fd Cos 180° Work = (F)(d)(-1) Work = -Fd |