Page 33 - Electrostatics-11

© GC Shiba

⃗⃗
⃗⃗
c) If vectors and act along the opposite direction, = 180°.
2
2
2
= + + 2 180°
= + − 2
2
2
= ( − ) ( − )
2
2
2
∴, = ( − ) ( − )
ℎ ℎ .
180°
, = −1 ( ) = −1 0 = 0
+ 180°
It means that the resultant vector moves in the direction of given vector of
greater magnitude.

2. Parallelogram law

It states that if the two vectors acting on a body be represented by the two adjacent

sides of the parallelogram drawn from a point, then the diagonal of the
parallelogram passing through the same point gives the resultant.

⃗⃗
⃗⃗
Let and be the two vectors acting on a body making an angle with each other.
⃗⃗
⃗⃗
The vectors and are represented by two sides AB and AE of the parallelogram
ABCE.
The

⃗⃗
diagonal AC of the parallelogram gives the resultant .

⃗⃗
⃗⃗
⃗⃗
i.e., = +
Draw CD perpendicular to AB produced in the figure. From right angle triangle
CBD,

10 Mechanics