JEE Main & Advanced Physics Motion in a Straight Line / सरल रेखा में गति Question Bank Self Evaluation Test - Motion in a Strainght Line

  • question_answer
    A point traversed half of the distance with a velocity \[{{v}_{0}}\]. The half of remaining part of the distance was covered with velocity \[{{v}_{1}}\] and second half of remaining part by \[{{v}_{2}}\] velocity. The mean velocity of the point, averaged over the whole time of motion is

    A) \[\frac{{{\text{v}}_{\text{0}}}\text{+}{{\text{v}}_{1}}+{{\text{v}}_{2}}}{3}\]           

    B) \[\frac{\text{2}{{\text{v}}_{\text{0}}}\text{+}{{\text{v}}_{1}}+{{\text{v}}_{2}}}{3}\]

    C) \[\frac{{{\text{v}}_{\text{0}}}\text{+.2}{{\text{v}}_{1}}+2{{\text{v}}_{2}}}{3}\]

    D) \[\frac{{{\text{v}}_{\text{0}}}\text{+2(}{{\text{v}}_{1}}+{{\text{v}}_{2}})}{\text{(2}{{\text{v}}_{\text{0}}}\text{+}{{\text{v}}_{1}}+{{\text{v}}_{2}})}\]

    Correct Answer: D

    Solution :

    Let the total distance be d. Then for first half distance, time \[=\frac{\text{d}}{\text{2}{{\text{v}}_{\text{0}}}}\], next distance. = \[{{v}_{1}}t\]and last half distance = \[{{v}_{2}}t\] \[{{\text{v}}_{\text{1}}}\text{t+}{{\text{v}}_{\text{2}}}\text{t=}\frac{\text{d}}{\text{2}};\text{ t=}\frac{d}{2\left( {{v}_{1}}+{{v}_{2}} \right)}\] Now average speed \[t=\frac{d}{\frac{d}{2{{v}_{0}}}+\frac{d}{2\left( v{{  }_{1}}+{{v}_{2}} \right)}+\frac{d}{2\left( v{{  }_{1}}+{{v}_{2}} \right)}}\] =\[\frac{\text{2}{{\text{v}}_{\text{0}}}\left( \text{v}{{  }_{\text{1}}}\text{+}{{\text{v}}_{\text{2}}} \right)}{\left( \text{v}{{  }_{\text{1}}}\text{+}{{\text{v}}_{\text{2}}} \right)\text{+2}{{\text{v}}_{\text{0}}}}\]


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