Mathematics

Problem

A vertical metal rod of mass

0.20\,\text{kg}

and length

0.15\,\text{m}

is hung so that it can move freely upward between two rails. The rails are in a horizontal magnetic field of

0.50\,\text{T}

directed perpendicular to the rod. A current of

20\,\text{A}

passes downward through the rod. If a constant opposing force of

0.30\,\text{N}

acts on the rod due to friction, what will be its speed after

0.30\,\text{s}

, starting from rest? a)

5.2\,\text{m s}^{-1}

3.6\,\text{m s}^{-1}

6\,\text{m s}^{-1}

1.1\,\text{m s}^{-1}