Aparticle moves along a straight line and its position at time t is given by s(t)=2t3−27t2+84t where s is measured in feet and t in seconds. a) find the velocity (in ft/sec) of the particle at time t=0: 84 b) the particle stops moving twice, once when t=a and again when t=b where a

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,?