I was pondering this hypothetical scenario earlier, and didn't know how to deal with the physics exactly (I think it has to do with momentum in collisions):
You and a block with mass $1kg$ are initially at rest on a frictionless surface. You start running while pushing the block on this frictionless surface. You are heavier than the block, let's say $80kg$. You put your hands out in front of you fully extended, walk towards the block to start pushing this block with a force of $5N$, therefore object will start to immediately accelerate at $5 m/s^2$. However, you are applying this constant force over a time of $2$ seconds. So won't I have to accelerate myself increasingly faster than the object in order for my hands to apply that constant force of $5N$? Or would it be the same? I don't completely understand how I can apply a constant force on this block if it's accelerating. If this situation is hard to visualize, I'm thinking of it like a parent pushing a child on a swing with a constant force over a period of time except without there being any resistance force.