A) 1s
B) 7 s
C) 5 s
D) 3 s
Correct Answer: B
Solution :
Given, \[s=-35m,\,\,u=30\,m{{s}^{-1}},\] \[a=-g=-10\,m{{s}^{-2}}\] Using, \[s=ut+\frac{1}{2}\,a{{t}^{2}},\,\] \[-35=30t-5{{t}^{2}}\] \[\Rightarrow \] \[{{t}^{2}}-6t-7=0\] Using, \[s=ut+\frac{1}{2}a{{t}^{2}},\] we get \[-35=30t-5{{t}^{2}}\] \[\Rightarrow \] \[{{t}^{2}}-6t-7=0\] \[t=-1,\,7\] but \[t\] cannot be -ve, Hence, correct answer is t = 7 s.You need to login to perform this action.
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