Question

Two forces 5N and 20 N are acting at angle of 120°. Find magnitude of their resultant.​

Answer 1

Answer:

resultant = 5√13 magnitude

Answer 2

The key to solving vectors efficiently is our choice of frame of reference and the axis system.

Resultant, R is given by the formula,

$R = \sqrt{A^{2} + B {}^{2} + 2AB \: cos ∞}$

which in itself has a beautiful derivation!

So,

$R \: = \: \sqrt{5 {}^{2} + 20 {}^{2} + 2 \times 5 \times 20 \times \cos(120) }$

$R = \sqrt{325} \: N \:$