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9th Class Science Gravitation and Floatation Question Bank Gravitation IIT JEE Objective Problems

  • question_answer
    A wooden block of mass 10 gm is dropped from the top of a cliff 100 m high. Simultaneously a bullet of mass 10 gm is fired from the foot of the cliff upward with a velocity 100 m/s. The bullet and the wooden block will meet each other after a time of

    A)  10 s                      

    B)  0.5 s  

    C)  1 s   

    D)  7 s

    Correct Answer: C

    Solution :

      Let in time t bullet and block meet. The distance covered by the block moving in downward direction is \[{{h}_{1}}=\frac{1}{2}g{{t}^{2}}\]            Distance covered by the bullet is \[{{h}_{2}}=ut-\frac{1}{2}g{{t}^{2}}=100t-\frac{1}{2}g{{t}^{2}}\] \[{{h}_{1}}+{{h}_{2}}=100\] \[\frac{1}{2}g{{t}^{2}}+100t-\frac{1}{2}g{{t}^{2}}=100\] \[100t=100\]                      \[t=1\text{ }sec\]                            


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