AFMC AFMC Solved Paper-2011

  • question_answer
    A wheel of radius 5 cm rotates so, that the relationship between the angle of rotation of wheel radius and the time is described by the equation \[\phi =A+Bt+C{{t}^{2}}+D{{t}^{3}}\]where, D = 1 rad /s2. The change in tangential acceleration during each second of the motion for the point on the rim is

    A) 0.3 ms-2                               

    B)  0.03 ms-2

    C) 3 ms-2                                   

    D) 0.09 ms-2

    Correct Answer: A

    Solution :

    Given, \[\text{o }\!\!|\!\!\text{ }\,=A+Bt+C{{t}^{2}}+D{{t}^{3}}\] Angular velocity \[\omega =d\text{o}|/dt=\frac{d}{dt}(A+Bt+C{{t}^{2}}+D{{t}^{3}})\] \[=B+2Ct+3D{{t}^{2}}\] Acceleration \[\alpha =\frac{d\omega }{dt}=\frac{d}{dt}(B+2Ct+3D{{t}^{2}})\] \[\frac{d\alpha }{dt}=6D=6\times 1=6m/{{s}^{2}}\] Rate of change of tangential acceleration \[\left( \frac{d{{\alpha }_{t}}}{dt} \right)=\frac{d}{dt}(r\alpha )=r\frac{d\alpha }{dt}=5\times {{10}^{-2}}\times 6\] \[=0.3\,m/{{s}^{2}}\]


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