InterviewSolution
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InterviewSolution
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Two stones are thrown up simultaneously from the edge of a cliff ` 240 m ` high with initial speed of ` 10 m//s and 40 m//s` respectively . Which of the following graph best represents the time variation of relative position of the speed stone with respect to the first ? ( Assume stones do not rebound after hitting the groumd and neglect air resistance , take ` g = 10 m//s^(2))` ( The figure are schematic and not drawn to scale )A. .B. .C. .D. . |
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Answer» Correct Answer - C For the second stone time required to reach the ground is given by `y = ut - (1)/(2) g t^2` `- 240 = 40 t - (1)/(2) xx 10 xx t^2` :. `5t^2 - 40 t - 240 = 0` `(t - 12)(t + 8) = 0` :. `t = 12 s` For the first stone : `- 240 = 10 t - (1)/(2) xx 10 xx t^2` :. `- 240 = 10t - 5t^2` `5 t^2 - 10 t - 240 = 0` `(t - 8)(t + 6) = 0` `T = 8 s ` During first `8` seconds both stones are in are : :. `y_2 - y_1 = (u_2 - u_1) t = 30 t` So, graph of `(y_2 - y_1)` against `t` is a straight line. After `8` seconds. `y_2 = u_2 t - (1)/(2) g t^2 - 240` Stones two has acceleration with respect to stone one. Hence graph (c ) is the correct description. |
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