Question

Susan applies a horizontal force of 180N on a rope , which causes two blocks with masses of 20 kg and 40 kg to move to the right . All frictional force as well as the mass of the rope can be ignored . Draw the free body diagram for each crate and calculate the acceleration of the crates

Answer 1

since the rope presumably does not stretch, consider the two blocks as a single mass.
F = ma, so a = F/m = 180/(20+40) = 3 m/s^2