Correct option: (D) 90°
Explanation:
P(t) = A [j˄ cos kt – j˄ sin kt]
F = [{dp(t)} / {dt}]
F = (d / dt) A [i˄ cos kt – j˄ sin kt]
= A [– i˄ sin kt (k)– j cos kt (k)]
F = Ak [– i˄ sin kt – j˄ cos kt]
angle between two vectors is θ
cos θ = {(F ∙ P) / (|F| |P|)}
= A [{(j˄ cos kt – j˄ sin kt) ∙ Ak (– i˄ sin kt – j˄ cos kt)} / {|F||P|}]
= A2 k [{– sin kt cos kt + sin kt cos kt} / {|F| |P|}]
= A2k(0)
= 0
θ = cos–1(0)
θ = 90°