What are plane mirrors

Alfred pushes on a heavy box, but cannot move it. the box has a lot of inertia motion friction gravity

What is the force that opposes motion and works against the downward pull? a) friction b) gravity c) weight d) acceleration

During the experiment if you could triple the breakaway magnetic force with all other quantities left unchanged, what is the new value for the critical velocity if it was v0 (initial velocity), initially? (b) now if you halved the radius with all other quantities left unchanged, what is the new critical velocity if it was v0 (initial velocity), initially? (c) if during the experiment, critical velocity quadrupled with all other quantities left unchanged, what is the new breakaway force if its magnitude was initially f0,?