How much thrust does a rocket need to take off?

i would suppose that it's because the incline is greatest then..but i suppose rocket means "something unmanned lol". the idea i have in my head says something along the lines of, the object has a path of of travel and when its moving it has a projected path of travel. so if the propellant was to be cut off when the rocket is traveling 100mph, it's not just going to stop..it has energy yet to be released. also i believe that things weigh more the faster they are going, according to Einsteins theory of relativity. but when things aren't moving they don't have a projected path of travel that is anywhere else other than where it is, then. so probably because motion must be established, and once it is, the forward motion of the object aids the propellant, if you will..or is less resistance for the propellant.