I was thinking more so of contact force, rather than time to actually reach him [that's clearly irrelevant].
An instantaneous change in speed cannot happen - he isn't hit with the full force all at once. There's a minute amount of time where he feels the tip of the force and more as you go on until you feel the full 400N. In this case, time would be the time between these two 'force feels'.
An instantaneous change in speed cannot happen - he isn't hit with the full force all at once. There's a minute amount of time where he feels the tip of the force and more as you go on until you feel the full 400N. In this case, time would be the time between these two 'force feels'.