question_answer

A tank accelerates uniformly in upward direction with acceleration\[1\,m/{{s}^{2}}\]and contains water. A block of mass 1 kg and density 0.8 g/cc is held stationary inside the tank with the help of the string as shown in the figure. The tension in the string is [Take\[{{\rho }_{\text{water}}}=1000\,kg/{{m}^{3}}\]and\[g=10\,m/{{s}^{2}}\]]

A)  2.2 N                          

B)  2.75 N

C)  0                                

D)  3.47 N

Correct Answer: B

Solution :

Free body diagram of block is as shown in the figure. Let us make observations from the frame of the tank. For equilibrium of the block, \[V{{\rho }_{w}}(g+a)=T+mg+ma\] \[\Rightarrow \]\[\frac{m}{800}\times 1000\times (10+1)=T+m(10+1)\] \[\Rightarrow \]\[T=2.75\,N\] Hence, the correction option is [b].