Why must the cross-sectional area at the bottom of the sprue be less than the cross-sectional area at the top of the sprue during pouring

I'm having some difficulty seeing the diagram clearly.but the question says there's a net inward force on the object.so we know right away,  from newton's 2nd law of motion, thatthat baby is accelerating.  it doesn't even matter which way thenet force is pointing.  if there's any net force, then either theobject's speed or else its direction must be changing.

This is asking what you have learned in your studies i haven't read studies and i'm not able to read your mind..