Question

When liquid medicine of density rho is to be put in the eye, it is done with the help of a dropper. As the bylb on the top of the dropper is pressed. A drop frons at the opening of the dropper. We wish to estimate the size of the drop. We first assume that the drop formed at the opening is spherical because that requires a minimum increase in its surface energy, To determine the size. We calculate the net vertical force due to the surface tension T when the radius of the drop is R. when this force become smaller than the weight of the drop the drop gets detached from the dropper. If the radius of the opening of the dropper is r, the vertical force due to the surface tension on the drop of radiusR(assuming rlt ltR) is

Answer 1

The vertical force due to the surface tension on the drop of radius is (2πr²T)/R

Explanation:

The vertical component of the force is given as:

Fv = F sin θ

The value of force is given by the formula:

F = T × 2πr

sin θ = r/R

Now, the vertical component becomes,

Fv = (T × 2πr)(r/R)

Where,

T = Surface tension

R = Radius of drop

r = Radius of dropper

Now,

∴ Fv = (2πr²T)/R