A) 4.0 m/s
B) 5.0 m/s
C) 5.5 m/s
D) 4.8 m/s
Correct Answer: A
Solution :
If \[{{t}_{1}}\]and \[2{{t}_{2}}\] are the time taken by particle to cover first and second half distance respectively. \[{{t}_{1}}=\frac{x/2}{3}=\frac{x}{6}\] ?(i) \[{{x}_{1}}=4.5\ {{t}_{2}}\]and \[{{x}_{2}}=7.5\ {{t}_{2}}\] So, \[{{x}_{1}}+{{x}_{2}}=\frac{x}{2}\Rightarrow 4.5{{t}_{2}}+7.5{{t}_{2}}=\frac{x}{2}\] \[{{t}_{2}}=\frac{x}{24}\] ?(ii) Total time \[t={{t}_{1}}+2{{t}_{2}}=\frac{x}{6}+\frac{x}{12}=\frac{x}{4}\] So, average speed \[=4\ m/sec\].
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