As it is given here that two blocks are pulled towards right side with constant horizontal velocity.
Both blocks are given that moving with speed 2 m/s
Now we can say that by Newton's II law
F = ma
i.e. Net force on a system is product of its mass and acceleration
but as we can see that here two blocks are moving with constant speed so here as per definition of acceleration we will say
[tex]a = \frac{dv}{dt}[/tex]
As we know that v = constant
[tex]a = 0[/tex]
so here from 2nd law
[tex]F = 0[/tex]
so net force must be zero block A
So correct FBD must be "option A"
we should not represent any force on it
