Question

Three blocks $A,B$ and $C,$ of masses$4kg,2kg$ and $1kg$ respectively are in contact on a friction less surface, as shown .if a force of $14N$ is applied on the $4kg$ blocks, then the contact force between A and B is

• A. $50N$
• B. $20N$
• C. $10N$
• D. $6N$

Answer 1

The correct option is D $6N$

the acceleration due to force 14N,
F=ma
F/m =a
14/(4+2+1)
14/7
=2m/s2
the contact force between A and B is used to move the bodies B and C only.
F=ma
F=(2+1)2
F=3×2
=6N
Hence,
option $(D)$ is correct answer.