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JEE Main & Advanced Sample Paper JEE Main Sample Paper-1

  • question_answer
    A block moves up a \[30{}^\circ \] incline under the action of certain forces, three of which are shown in figure. \[\overrightarrow{{{F}_{1}}}\]is horizontal and of magnitude 40 N. \[\overrightarrow{{{F}_{2}}}\]is normal to the .plane and of magnitude 20 N. \[\overrightarrow{{{F}_{3}}}\]is parallel to the plane and of magnitude 30 N. Determine the work done by each force as the block (and point of application of each force) moves 80 cm up the incline.

    A)  28 J, 34.6 J, 24 J

    B)  28 J, 0 J, 24 J

    C)  24 J, 44 J, 15 J   

    D)  None of these

    Correct Answer: B

    Solution :

    The component of \[{{F}_{1}}\] along the direction of the displacement is \[{{F}_{1}}\cos {{30}^{o}}\] (40 N) x (0.866) = 34.6 N Hence, the work done by \[{{F}_{1}}\] is (34.6 N) (0.80 m) = 28 J. \[{{F}_{2}}\] does no work because, it has no component in the direction of the displacement. The component of \[{{F}_{3}}\] in the direction of the displacement is 30 N. Hence, the work done by \[{{F}_{3}}\] is (30 N) (0.80 m) = 24 J.


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