A) 2s
B) 5s
C) 7s
D) 9s
Correct Answer: C
Solution :
If is time taken to reach the ground, then from equation of motion \[s=ut+\frac{1}{2}\,g{{t}^{2}}\]. Here, \[u=-v\sin {{30}^{o}}=-50\times \frac{1}{2}=-25\,\,m/s\] \[g=10\,m/{{s}^{2}},s=70\,\,m\] \[\therefore \] \[70=-25\,t+\frac{1}{2}\times 10\times {{t}^{2}}\] \[\Rightarrow \] \[5\,{{t}^{2}}-25\,t-70=0\] \[\Rightarrow \] \[t=-2\,\,s\] or \[t=7\,\,s\] Since, - 2 s is not valid, therefore \[t=7\,s\]You need to login to perform this action.
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