申論題

3. A thin (and uniform) ring with mass=m and radius=R (i.e., it has line density λ=m/(2πR)) is on the plane of ˆn₁, and ˆn₂. As shown in the figure below (suppose ˆn₃ passes through the center of the ring), the mass of a small section is dm=λ*R*dθ. *