# Surface tension calculation problem

1. Apr 16, 2009

### the-matrix

1. The problem statement, all variables and given/known data
I need to calculate the surface tension of jelly (gelatine dessert) or jell-o, as it is known in the states.

My textbook defines surface tension as Y=F/L. Is this the equation I would use to calculate surface tension? If so, how?

Last edited: Apr 16, 2009
2. Apr 17, 2009

### rl.bhat

Take a microscope slide. Attach it to a weighting spring. Dip it in the jelly. Now try to pull it out carefully. Reading in the spring will start increasing. Note down the reading at the moment when the slide detaches from the jelly. Since there are two surfaces on the slide, length of the free surface of the jelly is equal to the double the length of the slide. So according to the definition of the surface tension Y = F/2L.

3. Apr 17, 2009

### the-matrix

So by reading you mean the length from the top of the spring to the microscopic slide?

4. Apr 17, 2009

### rl.bhat

No. The spring is used to measure the full due to surface tension. Here length is the length of the slide which is in contact with jelly.