A liquid medicine is dispensed by counting a certain number of drops using an ey
ID: 1479909 • Letter: A
Question
A liquid medicine is dispensed by counting a certain number of drops using an eye dropper. The surface tension of the liquid medicine changes from 0.07274 to 0.06959 n/m when going from 20 °C to 40 °C. and the density of the medicine changes from 998.2 to 992.2 kg m-3 kg/cubic meter. Assume the temperature of glass eye dropper is constant. By what fraction does the volume of a drop of medicine change due to the change from 20 to 40 °C (hint: derive the expression for the ratio of the volumes before plugging in numbers)?
Explanation / Answer
Drop leaves the dropper whent the frce due to gravity is just about equal to the force due to surface tension.
F(surface tension)= 2*pi*r* surface tension(T) , r radius of the dropper. force due to gravity = mass(m) * acceleration due to gravity(g)
mass= volume(v) * density(d)
vdg=2 *pi* r*T
V(40)*d(40)=2*pi*r*T(40)
V(40)/V(20)=T(40)*d(20)/T(20)*d(40)
Substitute the values
=0.06959X998.2/(.07274 X 992.2)
=.9625
change is 1-.9625=.0375
3.75%
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.