Question

3-71A 20mm diameter steel bar is to be used as a torsion spring. If the torsional stress in the bar is not to exceed 110 MPa when one end is twisted through an angle of 15 degrees, what must be the length of the bar

Answer 1

The right answer is "1.903 m".

Step-by-step explanation:

Given that,

`\tau =110 \ MPa`

`G=80 \ GPa`

`\Theta=15* (\pi)/(180)`

`=(\pi)/(12)`

`d=20 \ mm`

As we know,

⇒
`(\tau)/(r)=(G \Theta)/(L)`

Or,

⇒
`L=(G \theta r)/(\tau)`

`=(80* 10^3)/(110)* (\pi)/(12)* 10`

`=1903.9 \ mm`

or,

`=1.903 \ m`