I Why do droplets of condensation run at an angle on a plastic sheet?

AI Thread Summary
Droplets of condensation on a plastic sheet tend to run at angles rather than straight down, creating a pattern of tracks that are mostly parallel but can veer left or right. This behavior raises questions about the forces at play beyond gravity, with possible explanations including the influence of "stretch marks" in the plastic or external wind patterns. The plastic sheet, designed to reduce heat loss, is tautly stretched, which may affect how droplets move. The discussion also humorously suggests external weather conditions, like a passing tropical storm, as a potential factor. Overall, the angle of droplet movement remains a topic of curiosity and speculation.
xtempore
Messages
19
Reaction score
13
TL;DR Summary
I put some plastic sheeting over our single-glazed windows, to reduce heat loss. I was surprised to find that droplets of condensation didn't run straight down, but appeared to run at a fairly consistent angle - left or right.
I think the picture says it all! As the droplets of condensation reached a certain size they begin to run down the plastic sheet, but rather than just running straight down, they veer off to the left or right. Most of the tracks are at fairly much parallel, with some exceptions, and the pattern can go either left or right, but the angle looks to be similar.

So, obviously gravity is acting as a force, straight down, so what force is causing these droplets to run at angles? And why that reasonably consistent angle?

The plastic sheeting is meant to reduce heat loss. It's stuck to the window frame with double-sided tape, and there is a space between the plastic and the glass (basically a cheap version of double-glazing). The plastic is then stretched taut by using a hair-dryer to remove any wrinkles.

Any ideas?

weird-droplet-tracks.jpg
 
  • Like
Likes vanhees71 and Drakkith
Physics news on Phys.org
Shrinkwrap sheets come pre-stretched in a number of directions, the normally jumbled up molecules locked to each other. Heating it up unlocks the bonds, returning the molecules to being jumbled up, again, and "shrinking" the sheet.

The water droplets are traveling down "stretch marks".
 
Last edited:
  • Like
Likes russ_watters, anorlunda and vanhees71
Alternate theory: a very consistent wind blowing past your house from the left, then switching to from the right.

Maybe a tropical storm just passed directly over you.

:oldbiggrin:
 
Consider an extremely long and perfectly calibrated scale. A car with a mass of 1000 kg is placed on it, and the scale registers this weight accurately. Now, suppose the car begins to move, reaching very high speeds. Neglecting air resistance and rolling friction, if the car attains, for example, a velocity of 500 km/h, will the scale still indicate a weight corresponding to 1000 kg, or will the measured value decrease as a result of the motion? In a second scenario, imagine a person with a...
Dear all, in an encounter of an infamous claim by Gerlich and Tscheuschner that the Greenhouse effect is inconsistent with the 2nd law of thermodynamics I came to a simple thought experiment which I wanted to share with you to check my understanding and brush up my knowledge. The thought experiment I tried to calculate through is as follows. I have a sphere (1) with radius ##r##, acting like a black body at a temperature of exactly ##T_1 = 500 K##. With Stefan-Boltzmann you can calculate...
Thread 'Griffith, Electrodynamics, 4th Edition, Example 4.8. (First part)'
I am reading the Griffith, Electrodynamics book, 4th edition, Example 4.8 and stuck at some statements. It's little bit confused. > Example 4.8. Suppose the entire region below the plane ##z=0## in Fig. 4.28 is filled with uniform linear dielectric material of susceptibility ##\chi_e##. Calculate the force on a point charge ##q## situated a distance ##d## above the origin. Solution : The surface bound charge on the ##xy## plane is of opposite sign to ##q##, so the force will be...
Back
Top