Figure shows a U-tube of uniform cross-sectional area A. Let the liquid be depressed through the distance y in a limb, the difference of levels between two limbs will be 2 y as shown in figure
The liquid now oscillates about the initial positions.
Excess pressure on whole liquid = (excess height of the liquid column) (density) (g)
`= 2y xx 1 xx g` (as density of water `= 1`)
Restoring Force on the liquid = Pressure x area of cross-section `= 2ygA`
Due to this force the liquid acclerates and if its acceleration is a, we have `ma = 2ygA`
Do to this force the liquid accelerated and if its acceleration is a, we have `ma = -2ygA`
`rArr (2 xx 30 xx A) a = - 2ygA rArr a = - (g)/(30) y`
`T = (2pi)/(omega) = 2omegasqrt((30/g)) = 2pisqrt((30/980))` [as `omega = sqrt((g)/(30))`] `= 1.098` second