A 6.4-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 tensionin the string.