Two rods `A` and `B`, each of equal length for different materials are suspended from a common support as shown in the figure. The rods `A` and `B` can support a maximum load of `W_(1)=600N` and `W_(2)=6000N` respectively. If their cross sectional area are `A_(1)=10mm^(2)` and `A_(2)=1000mm^(2)`, respectively then identify the stronger material.

Explanation

At first sight, it looks thar rod `B` is stronger as it supports a larger load. But we canot compare strengths without having a common basis of comparison. Since the rods have different cross sectional area, therefore, the strengths can be compared by determining the load capacity per unit area.
For rod A
`sigma_(1)=(W_(1))/(A_(1))=(600N)/(10mm^(2))=600/(10xx10^(-6))=60xx10^(6)Nm^(-2)`
For rod `B`
`sigma_(2)=(W_(2))/(A_(2))=(6000N)/(1000mm^(2))=6000/(1000xx10^(-6))=6xx10^(6)Nm^(-2)`
Since `sigma_(1)gtsigma_(2)` therefore, the material of rod `A` is stronger than that of rod `B`.