question_answer

Three blocks A, B and C of masses 4 kg, 2 kg   and 1 kg respectively, are in contact on a 1   frictionless surface, as shown. If a force of 14 N is applied on the 4 kg block, then the contact force between A and B is  [NEET 2015 ]

A) 2 N

B) 6 N

C) 8 N

D) 18 N

Correct Answer: B

Solution :

Given, \[{{m}_{A}}=4\,kg\]

So total mass \[(M)=4+2+1=7kg\]

Now,     \[F=Ma\Rightarrow 14=7a\Rightarrow a=2m/{{s}^{2}}\]

FED of block A,

\[F=F'=4a\Rightarrow F'=14-4\times 2\Rightarrow F'=6N\]