Question

A 80 mm diameter shaft transmits power at maximum shear stress of 60 MPa when the stress in key is 50 MPa, the length of key if it is 20 mm wide , will be

• A. 150.8 mm
• B. 75.4 mm
• C. 301.6
• D. 180.2

Answer 1

The correct option is A 150.8 mm

Let length of key = $l$ mm

then , $\frac{\pi }{16}\times {\tau }_{{}_3}\times (d{)}^3=\frac{l.b.{\tau }_{A}d}{2}$

$\frac{\pi }{16}\times 60\times (80{)}^3=\frac{l\times 20\times 50\times 80}{2}$

$l=150.8mm$