Object I is a solid cylinder with diameter d has resistance R. What would be resistance of another object made of the same material and with the same mass as Object I but has the cross section shown below (it is a hollow cylinder with outer diameter 2d and inner diameter d).

Question

Object I is a solid cylinder with diameter d has resistance R. What would be resistance of another object made of the same material and with the same mass as Object I but has the cross section shown below (it is a hollow cylinder with outer diameter 2d and inner diameter d).
R/9
9R
R
R/3
3R

Elena · Answer

R=ρL/A R =4ρL/πd² R₁ =4ρL/ (π4d²- πd²) =4ρL/ 3πd² R₁=R/3