A) 0.5 s
B) 1.5 s
C) 3.5 s
D) 3.4 s
Correct Answer: B
Solution :
From equation of motion \[{{v}^{2}}={{u}^{2}}+2\,g\,h\] where v is final velocity, u is initial velocity and his height. Given, \[h=4.9\,\,m,\,g=9.8\,m/{{s}^{2}},u=0\] \[\therefore \] \[v=\sqrt{2\,gh}\] \[=\sqrt{2\times 9.8\times 4.9}=9.8\,m/s\] Coefficient of restitution (e) of an object is a unit fraction value representing the ratio of velocities before and after an impact. \[\therefore \] \[v=\frac{3}{4}\times 9.8\] Time taken from first bounce to second bounce is \[t=\frac{2\,v}{g}=2\times \frac{3}{4}\times 9.8\times \frac{1}{9.8}=1.5\,s\]
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