A) 5 s
B) 4 s
C) 2 s
D) 3 s
Correct Answer: D
Solution :
If ball is falling for t s and distance travelled by it be S metre before observation. Then, distance travelled in \[(t +2)s=-\,(S +78.4) m\] So, \[\operatorname{S}=\frac{1}{2}\,\times 9.8\times {{t}^{2}}\] ... (i) and \[(S+78.4)\,\,=\,\,\frac{1}{2}\times 9.8{{(t+2)}^{2}}\] ... (ii) On solving Eqs. (i) and (ii), we have \[t= 3\,\,s\]You need to login to perform this action.
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