$10-85.$ The shaft is made of red brass C$83400$ copper and has an elliptical cross section. If the allowable shear stress is ${}_{\text{a}\text{l}\text{l}\text{o}\text{w}}=20$MPa, and the relative angle of twist is limited to $2\mathrm{.}50,$ determine the dimensions a and $b.$ Take $a=2b.$

Probs. $10-84/85$

$10-85.$ The shaft is made of red brass C$83400$ copper and has an elliptical cross section. If the allowable shear stress is ${}_{\text{a}\text{l}\text{l}\text{o}\text{w}}=20$MPa, and the relative angle of twist is limited to $2\mathrm{.}50,$ determine the dimensions a and $b.$ Take $a=2b.$

Probs. $10-84/85$