RAJASTHAN PMT Rajasthan - PMT Solved Paper-2006

  • question_answer
    A body falls from a height h = 200 m. The ratio of distance travelled in each 2 s, during t = 0 to t = 6 s of the journey is:

    A)  1 : 4 : 9                                

    B)         1 : 2 : 4                

    C)         1 : 3 : 5                                

    D)         1 : 2 : 3

    Correct Answer: C

    Solution :

    Using the relation                 \[s=ut+\frac{1}{2}g{{t}^{2}}\] As the body is falling from rest,\[u=0\]                 \[s=\frac{1}{2}g{{t}^{2}}\] Suppose the distance travelled in                 \[t=2s,\,\,t=4s,\,\,t=6s\] are \[{{s}_{2}},\,\,{{s}_{4}}\] and \[{{s}_{6}}\] respectively. Now,     \[{{s}_{2}}=\frac{1}{2}g{{(2)}^{2}}=2\,\,g\]                 \[{{s}_{4}}=\frac{1}{2}g{{(4)}^{2}}=8\,\,g\]                 \[{{s}_{6}}=\frac{1}{2}g{{(6)}^{2}}=18\,\,g\] Hence, the distance travelled in First two seconds                 \[{{({{S}_{i}})}_{2}}={{s}_{2}}-{{s}_{0}}=2\,\,g\]                 \[{{({{s}_{m}})}_{2}}={{s}_{4}}-{{s}_{2}}\]                 \[=8\,\,g-2\,\,g\]                 \[=6\,\,g\]                 \[{{({{s}_{f}})}_{2}}={{s}_{6}}-{{s}_{4}}\]                 \[=18\,\,g-8\,\,g\]                 \[=10\,\,g\] Now, the ratio becomes \[=2g:6g:10s\] \[=1:3:5\]


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