Question

A 15-mm-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 30°, what must be the length of the bar?

Answer 1

The length of bar will be 2.82 m

Step-by-step explanation:

Given that

d= 15 mm

r= 7.5 mm

Shear stress = 110 MPa

θ = 30° (30° = 30° x π/180° =0.523 rad)

θ = 0.523 rad

G for steel

G= 79.3 GPa

We know that

`(\tau)/(r)=(G\theta )/(L)`

`(110)/(7.5* 10^(-3))=(79.3* 10^3* 0.523 )/(L)`

L= 2. 82 m

The length of bar will be 2.82 m