A journal bearing has a shaft diameter of $$40mm$$ and a length of $$40mm.$$ The shaft is rotating at $$20$$ $$rad/s$$ and viscocity of the lubricant is $$20mPa.s.$$ The clearance is $$0.020mm.$$ The loss of the torque due to viscocity of the lubricant is approximately

A natural feed journal bearing of diameter $$50mm$$ and length $$50mm$$ operating at $$20$$ revolutions/sec carries a load of $$2kN$$. The lubricant used has a viscosity of $$20mPa$$-$$s$$. The radial clearance is $$50\mu m.$$ The Sommerfeld number for the bearings is

A ball bearing operating at a load $$F$$ has $$8000$$hours of life. The life of the bearing, in hours, when the load is doubled to $$2F$$ is

The life of a ball bearing at a load of $$10$$ $$kN$$ is $$8000$$ hours. Its life in hours, if the load is increased to $$20$$ $$kN,$$ keeping all other conditions same, is