Question

The expected life of a ball bearing subjected to a load of 9800 N and working at 1000 rpm is 3000 hours. What is the expected life of the same bearing for a similar load of 4900 N and speed of 2000 rpm?

• A. Unchanged
• B. $6000$ hours
• C. $12000$ hours
• D. $1500$ hours

Answer 1

The correct option is C $12000$ hours

$L(P{)}^3=\text{Constant}$
$\frac{L_1}{L_2}={\left(\frac{P_2}{P_1}\right)}^3$
$\Rightarrow \frac{1000\times 60\times 3000}{2000\times 60\times t_2}={\left(\frac{4900}{9800}\right)}^3$
$t_2=12000hrs$