Haryana PMT Haryana PMT Solved Paper-2010

  • question_answer
    A body falls freely from the top of a tower. It covers 36% of the total height in the last second before striking the ground level. The height of the tower is

    A)  50m                                     

    B)  75m

    C)  100m                                   

    D)  125m

    Correct Answer: D

    Solution :

                    Let height of tower is h and body takes time t to reach the ground when it falls freely. \[\therefore \]  \[h=\frac{1}{2}g{{t}^{2}}\]               ...(i) In last second ie, tth sec body travels \[=0.36h\] It means in rest of the time ie, in \[(t-1)sec\]it travels   \[=h-0.36\text{ }h=0.64\text{ }h\] Now, applying equation of motion for \[(t-1)sec\] \[0.64\,h=\frac{1}{2}g{{(t-1)}^{2}}\]       ....(ii) From Eqs. (i) and (ii), we get \[t=5s\]and \[h=125m\]


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