Needing explaining ! (2 pics attached)

28. the pressure is greater outside the tube (D) than inside the tube(B). this is because when (A) is pressed it forces air out through (C). Spraying causes a region of low pressure inside the tube (B). This difference in pressure causes the rise of the concentrated fertilizer solution into the chamber which in turn is sprayed and the process continues.

27. momentum is the product of mass and the velocity of a particle.

momentum= mv where m is the mass in kg  and v the velocity in m/s

thus from the question, m= 38kg v= 2.2m/s

therefore momentum=38kg×2.2m/s

                                    =83.8kgm/s