2. Questions Bank
  3. 9th Class
  4. Science
  5. Work and energy

9th Class Science Work and energy Question Bank Work, Energy and Power

  • question_answer
    The bag of sand of mass 2 kg is suspended by a rope. A bullet of mass 10 g is fired at it and gets embedded into it. The bag rises up a vertical height of 10 cm. The initial velocity of the bullet is nearly

    A)  70 m/s           

    B)         140 m/s

    C)  210 m/s          

    D)         280 m/s  

    Correct Answer: D

    Solution :

     Final velocity,\[v=\sqrt{2gh}\]                 \[=\sqrt{2\times 9.8\times 0.1}=1.4\,\,m/s\] From conservation of momentum,                 \[0.01\,\,v+0=(2+0.01)\times 1.4\] \[\therefore \]  \[u=201\times 1.4]=281.4\]                  \[\approx \mathbf{280}\,\,\mathbf{m/s}\].


You need to login to perform this action.
You will be redirected in 3 sec spinner