consider the given question
A wooden block of mass 2 kg rests on a soft horizontal floor.when an iron cylinder of mass 25 kg is placed on the top of the block,the floor yields downward with a acceleration of 0.1m/s^2.Here I want to ask that as the downward force is 270 N,so this much force will be applied on table, what will be the reaction of table on the box by newton's third law.Moreover if there is an acceleration it will be upward and gravitational force will be downward,so what will be the acceleration box.
thank you

So this means the floor "resists" with a force that is less than the weight of the block + cylinner. If we use g= 10m/s^2, the upward force from the floor is mg-ma, or 27 Kg(10m/s^2 - 0.1m/s^2) = 267.3 N.

Actually the downward force between the box and table is 270N - ma = 270N- (27Kg x 0.1m/s^2) = 267.3N, which is the same as calculated above. This is also the upward force of the table acting on the box.

But as you've described it the:soft floor" can't hold the weight of the box and cylinder, so the acceleration is downward, not upward. The initial premise here is that the acceleration is downward at 0.1m/s^2.