MCQ
A particle is acted simultaneously by mutually perpendicular simple hormonic motions $\text{x}=\text{a}\cos\omega\text{t}\ \text{and}\ \text{y}=\text{a}\sin\omega\text{t}.$ The trajectory of motion of the particle will be:
    • A
      An ellipse.
    • B
      A parabola.
    • C
      A circle.
    • D
      A straight line.

    Answer

    1. A circle.

    Explanation:

    Resultant displacement is x + y

    $\text{x}=\text{a}\cos\omega\text{t}\ ...(1)$

    $\text{y}=\text{A}\sin\omega\text{t}\ ...(2)$

    Dispacement $=\text{a}\cos\omega\text{t}+\text{a}\sin\omega\text{t}$

    $\text{y}'=\text{a}\sqrt{2}\Big[\frac{\cos\omega\text{t}}{\sqrt{2}}+\frac{\sin\omega\text{t}}{\sqrt{2}}\Big]$

    $\text{y}'\text{a}\sqrt{2}\ [\cos\omega\text{t}\cos45^\circ+\sin\omega\text{t}\sin45^\circ]$as the particle is acted simultaneously by Mutually perpendicular direction.

    $\text{y}'=\text{a}\sqrt{2}\cos\text{s}(\omega\text{t}-45^\circ)$

    Hence the displacement is neither a straight line nor a parabola.

    Now, squaring and adding (i), (ii)

    $\text{x}^2+\text{y}^2=\text{a}^2\cos^2\omega\text{t}+\text{a}^2\sin^2\omega\text{t}=\text{a}^2[\cos^2\omega\text{t}+\sin^2\omega\text{t}]$

    $\text{x}^2+\text{y}^2=\text{a}^2$

    This shows the equation of circle, hence the motion is circular motion.

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