A) \[\sqrt{\frac{2.7}{9.8}s}\]
B) \[\sqrt{\frac{5.4}{9.8}s}\]
C) \[\sqrt{\frac{5.4}{8.6}s}\]
D) \[\sqrt{\frac{5.4}{11}s}\]
Correct Answer: D
Solution :
Key idea: Net acceleration on the elevator car is more than acceleration due to gravity. Since elevator car is ascending upwards, from Newton?s second law, the net force is acting upwards, hence resultant acceleration is \[{{a}_{r}}=\left( g+a \right)\] \[=\left( 9.8+1.2 \right)=11\,\,m/{{s}^{2}}\] Relative velocity of observer to elevator is \[{{u}_{r}}=0\] From the equation \[s={{u}_{r}}t+\frac{1}{2}{{a}_{r}}{{t}^{2}}\] \[2.7=0+\frac{1}{2}\times 11\times {{t}^{2}}\] \[\Rightarrow \] \[{{t}^{2}}=\frac{5.4}{11}\] \[\Rightarrow \] \[t=\sqrt{\frac{5.4}{11}s}\]You need to login to perform this action.
You will be redirected in
3 sec