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NEET Sample Paper NEET Sample Test Paper-91

  • question_answer
    A body of mass 5 kg under the action of constant force \[\overset{\to }{\mathop{F}}\,={{F}_{x}}\hat{i}+{{F}_{y}}\hat{j}\] has velocity at \[t=0\,s\] as \[\overset{\to }{\mathop{v}}\,=\left( 6\hat{i}-2\hat{j}\,\,m/s \right)\] and at \[t=10\,s\] as\[\overset{\to }{\mathop{v}}\,=+6\hat{j}\,m/s.\] The force \[\overset{\to }{\mathop{F}}\,\] is:

    A) \[\left( -3\hat{i}+4\hat{j} \right)N\]                      

    B) \[\left( -\frac{3}{5}\hat{i}+\frac{4}{5}\hat{j} \right)N\]

    C) \[\left( 3\hat{i}-4\hat{j} \right)N\] 

    D)        \[\left( \frac{3}{5}\hat{i}-\frac{4}{5}\hat{j} \right)N\]

    Correct Answer: A

    Solution :

    [a] From question, Mass of body, m = 5 kg Velocity at t = 0, \[u=(6\hat{i}-2\hat{j})\,\,m/s\] Velocity at t = 10s, \[v=+6\hat{j}\,\,m/s\] Force, F = ? Acceleration, a \[=\frac{v-u}{t}\] \[=\frac{6\hat{j}-(6\hat{i}-2\hat{j})}{10}=\frac{-3\hat{i}+4\hat{j}}{5}m/s\] Force, F = ma \[=5\times \frac{(-3\hat{i}+4\hat{j})}{5}=(-3\hat{i}+4\hat{j})N\]


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