NEET Physics NLM, Friction, Circular Motion NEET PYQ-NLM Friction Circular Motion

  • question_answer
    A stone tied to the end of a string of 1 m long is whirled in a horizontal circle with a constant speed. If the stone makes 22 revolutions in 44 s, what is the magnitude and direction of acceleration of the stone?    [AIPMT (S) 2005]

    A) \[\frac{\pi }{2}\,m{{s}^{-2}}\] and direction along the radius towards the centre

    B) \[{{\pi }^{2}}\,m{{s}^{-2}}\] and direction along the radius away from centre

    C) \[{{\pi }^{2}}\,m{{s}^{-2}}\] and direction along the radius towards the centre

    D) \[{{\pi }^{2}}\,m{{s}^{-2}}\] and direction along the tangent to the circle

    Correct Answer: C

    Solution :

    Since, speed is constant throughout the motion, so it is a uniform circular motion. Therefore, its radial acceleration
                            \[a=r{{\omega }^{2}}\]
                            \[=r{{\left( \frac{2\pi n}{t} \right)}^{2}}=r\times \frac{4{{\pi }^{2}}{{n}^{2}}}{{{t}^{2}}}\]
                            \[=\frac{1\times 4\times {{\pi }^{2}}\times {{(22)}^{2}}}{{{(44)}^{2}}}\]
                            \[={{\pi }^{2}}m/{{s}^{2}}\]
    This acceleration is directed along radius of circle.


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