KVPY Sample Paper KVPY Stream-SX Model Paper-13

  • question_answer
    A particle moves constantly in a circle centered at the origin with a period T. If its position at time \[t=0\] seconds is (A, 0) meters, which graph represents \[{{v}_{x}},\] the x-component of the particle's velocity, as a function of time?

    A)

    B)

    C)

    D)

    Correct Answer: D

    Solution :

    Based on the description of the particle?s position at time \[t=0,\] we know that the equation that describes the particle?s x-coordinate as a function of time is  \[x=A\cos (\omega t)\] To determine the x-component of the velocity, we take the time derivative of this function: \[{{v}_{x}}=\frac{dx}{dt}=\frac{d}{dt}A\,\,\cos (\omega t)=-\,\omega A\,\,\sin \,\,(\omega t)\] This is essentially a negative sine function, which matches the graph in answer 4. The problem may be solved conceptually, too, by considering the x-component of the rotating particle as a mass on a horizontally-stretched spring. The mass is released from a position +A at time t=0, at which point it begins to accelerate in the x-direction, beginning a simple harmonic oscillation. This motion is consistent with answer.


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