question_answer

Two blocks A and B of masses 10 kg and 20 kg respectively are connected by a massless spring as shown in figure. A force of 200 N acts on the block B. At the instant shown, the block A has an acceleration of \[12\,m/{{s}^{2}}\]The acceleration of the block B will be

A)                  zero                     

B)                  \[4\,m/{{s}^{2}}\]

C)  \[10\,m/{{s}^{2}}\]                        

D)  \[12\,m/{{s}^{2}}\]

Correct Answer: B

Solution :

                A has acceleration of \[12\,m/{{s}^{2}}\] \[\therefore \]                  \[12\times 10=kx\] Now, for block B,                 \[k\,x=200-20\,a\] \[\Rightarrow \]               \[20\,a=200-120\] \[\Rightarrow \]                               \[a=4\,m/{{s}^{2}}\]