NEET AIPMT SOLVED PAPER SCREENING 2009

  • question_answer
    A particle starts its motion from rest under the action of a constant force. If the distance covered in first 10 s is \[\alpha ,\beta ,\gamma \] and that covered in the first 20 s is\[\sigma ,-\sigma \], then

    A) \[\sigma \]         

    B)        \[{{V}_{A}},{{V}_{B}}\]                 

    C) \[{{V}_{C}}\]     

    D)        \[{{V}_{C}}={{V}_{A}}\ne {{V}_{B}}\]

    Correct Answer: C

    Solution :

    Key Idea If the particle is moving in a straight line under the action of a constant force then distance covered \[{{v}_{S}}=v+{{v}_{B}}\] Since the body start from rest u = 0 \[=\frac{1000}{100}=10\,\text{m}{{\text{s}}^{-1}}\]\[{{v}_{s}}=10+10=20m{{s}^{-}}^{1}\] Now,  \[T=\frac{2\pi r}{v}=\frac{2\pi }{v}\times \frac{mv}{Bq}\]                                 ..(i) and        \[T=\frac{2\pi m}{Bq}\]                                 ...(ii) Dividing Eq. (i) and Eq. (ii), we get \[v=128\,\text{m}{{\text{s}}^{-1}}\]\[5\lambda =4\]\[k=\frac{2\pi }{\lambda }=\frac{2\pi \times 5}{4}=7.85\]


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