Why does a small piece of steel rod sinks while a large steel oil tanker floats? Plss help thanks! pls include EXPLANATION and EXAMPLES that I can proof to people that has no knowledge ​​

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,?