Question

The resultant of two forces, one double the other in magnitude, is perpendicular to the smaller of the two forces. The angle between the two forces is –

• A. $120^{0}$
• B. $60^{0}$
• C. $90^{0}$
• D. $150^{0}$

Answer 1

Answer: (A)

$120^{0}$

Answer 2

Given that $\left( \overset{\rightarrow}{F_{1}} + \overset{\rightarrow}{F_{2}} \right)$. $\overset{\rightarrow}{F_{1}}$ = 0

where F₁ < F₂

\ $F_{1}^{2}$+ F₁ F₂ cos q = 0

Given that F₂ = 2F₁

$F_{1}^{2}$ + $2F_{1}^{2}$ cos q = 0

cosq = –$\frac{1}{2}$

s\ q = 2p/3