A) \[2\sqrt{10}s\]
B) 5 s
C) 10 s
D) \[\sqrt{10}s\]
Correct Answer: C
Solution :
Momentum before explosion = Momentum after explosion \[m\times 200\hat{j}=\frac{m}{2}\times 400\hat{j}+\frac{m}{2}v\] \[=\frac{m}{2}\left( 400\hat{j}+v \right)\]\[\Rightarrow \]\[400\hat{j}-400\hat{j}=v\] \[\therefore \]\[v=0\] i.e., the velocity of the other part of the mass, v = 0 Let time taken to reach the earth by this part be t Applying formula, \[h=ut+\frac{1}{2}g{{t}^{2}}\] \[490=0+\frac{1}{2}\times 9.8\times {{t}^{2}}\]\[\Rightarrow \]\[{{t}^{2}}=\frac{980}{9.8}=100\] \[\therefore \]\[t=\sqrt{100}=10\sec \]You need to login to perform this action.
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