Question

Two identical ball bearings P and Q are operating at loads 30 kN and 45 kN respectively. The ratio of the life of bearing P to the life of bearing Q is

• A. $\frac{9}{4}$
• B. $\frac{3}{2}$
• C. $\frac{27}{8}$
• D. $\frac{81}{16}$

Answer 1

The correct option is C $\frac{27}{8}$

$L={\left(\frac{C}{P}\right)}^3$
where L= Lifeof bearing
P= Load
$\frac{{\text{(Life)}}_P}{{\text{(Life)}}_Q}=\frac{{\text{(Load)}}_Q^3}{{\text{(Load)}}_P^3}={\left[\frac{45}{30}\right]}^3=3.375or\frac{27}{8}$