JCECE Medical JCECE Medical Solved Paper-2011

  • question_answer
    A parachutist drops first freely from an aero plane for 10 s and then parachute opens out. Now he descends with a net retardation of \[2.5\,m/{{s}^{2}}.\] If he bails out of the plane at a height of 2495 m and\[g=10\,m/{{s}^{2}},\] his velocity on reaching the ground will be

    A)  5 m/s            

    B)  10 m/s

    C)  15 m/s          

    D)  20 m/s

    Correct Answer: A

    Solution :

     The velocity v acquired by the parachutist after 10 s \[v=u+gt=0\] \[=0+10\times 10=100\,m/s\] Then, \[{{S}_{1}}=ut+\frac{1}{2}g{{t}^{2}}\] \[=0+\frac{1}{2}\times 10\times {{10}^{2}}\] \[=500\,m\] The distance travelled by the parachutist under retardation. \[{{S}_{2}}=2495-500=1995\,m\] Let \[{{v}_{g}}\]be this velocity an reaching the ground. Then      \[v_{g}^{2}-{{v}^{2}}=2a{{s}_{2}}\] or \[v_{g}^{2}-{{(1000)}^{2}}=2\times (-2.5)\times 1995\] \[{{v}_{g}}=5m/s\]


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