Question

Given :$\overset{\rightarrow}{P} = \overset{\rightarrow}{A} - \overset{\rightarrow}{B}$ and P = A + B. The angle between $\overset{\rightarrow}{A}$ and $\overset{\rightarrow}{B}$ is –

• A. (a)$0^{0}$
• A. (b)$90^{0}$
• A. (c)$180^{0}$
• A. (d)$270^{0}$

Answer 1

(c)

(A + B) = $\sqrt{A^{2} + B^{2} - 2AB\cos\theta}$

A² + B² + 2AB = A² + B² – 2AB cos q

2AB (1 + cos q) = 0

cos q = – 1

q = 180⁰