A pair of spur gears with module $$5$$ $$mm$$ and a center distance of $$450mm$$ is used for a speed reduction of $$5:1$$. The number of teeth on pinion is _________

A hydrodynamic journal bearing is subject to $$2000$$ $$N$$ load at a rotational speed of $$2000$$ $$rpm.$$ Both bearing bore diameter and length are $$40mm.$$ If radial clearance is $$20\mu m$$ and bearing is lubricated with an oil having viscosity $$0.03$$ $$Pa.s,$$ the Sommerfeld number of the bearing is _______

The major difficulty during welding of aluminium is due to its

An aluminium alloy (density $$2600$$ $$kg/{m^3}$$ ) casting is to be produced. A cylindrical hole of $$100$$ $$mm$$ diameter and $$100$$ $$mm$$ length is made in the casting using sand core (density $$1600$$ $$kg/{m^3}$$ ). The net buoyancy force (in Newton) acting on the core is _____________________