A square plate of 20 cm side moves over another plate with velocity `5 cm s^(-1)`, both plates immersed in water. If the viscous force is `0.205 gf` and viscosity of water is 0.01 poise, what is the separation between the plates?

Explanation

Area of plate, `A= 20 xx 20 `
`= 400 cm^(2)`
`d upsilon = 5 cm s^(-1), F=0.205 gf`
`= 0.205 xx 980 dyn e`,
`eta = 0.01 poise , dx = ?`
Now `F= eta A (d upsilon)/(dx) or dx = (eta A d upsilon)/(F)`
`:. Dx = (0.01 xx 400 xx 5)/(0.205 xx 980) = 0.1 cm`.