A6.4-n force pulls horizontally on a 1.5-kg block that slides on a smooth horizontal surface. this block is connected by a horizontal string to a second block of mass m2=0.93 kg on the same surface, what is the acceleration of the blocks? what is the tension of the string?

-- Although it's not explicitly stated in the question,we have to assume that
the surface is frictionless.  I guess that's what "smooth" means.

-- The total mass of both blocks is (1.5 + 0.93) = 2.43 kg. Since they're
connected to each other (by the string), 2.43 kg is the mass you're pulling.

-- Your force is 6.4 N.
                                    Acceleration = (force)/(mass) = 6.4/2.43 m/s²
                                                                 That's about  2.634 m/s² 

(I'm going to keep the fraction form handy, because the acceleration has to be
used for the next part of the question, so we'll need it as accurate as possible.)

-- Both blocks accelerate at the same rate. So the force on the rear block (m₂) is

       Force = (mass) x (acceleration) = (0.93) x (6.4/2.43) = 2.45 N.

That's the force that's accelerating the little block, so that must be the tension
in the string.

B. convex since the words are bigger