Droplet of ballpoint ink in water (why)

Click For Summary

Discussion Overview

The discussion revolves around the behavior of a droplet of ballpoint ink when placed on water, exploring the reasons for its floating and movement. Participants consider various physical properties and phenomena that may influence this behavior, including density, viscosity, surface tension, and Brownian motion.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant suggests that if the ink droplet is floating, its density must be less than that of water.
  • Another participant proposes that the ink's hydrophobic nature and its lightness may prevent it from breaking the surface tension, which could also lead to movement due to variations in force potentials, including electrostatic forces.
  • A different viewpoint introduces the idea that Brownian motion might play a role in the droplet's behavior.
  • Another participant posits that the surface tension of the water could be supporting the droplet, causing it to move back and forth due to minor disturbances on the water's surface.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the factors influencing the behavior of the ink droplet, indicating that the discussion remains unresolved.

Contextual Notes

Participants have not reached a consensus on which specific factors are most significant, and the discussion includes various assumptions about the properties of the ink and water.

Willsr
Messages
1
Reaction score
0
I was wondering, a ballpoint pen ink droplet is droped on water, it floats and moves, why?
Is it density, viscosity, surface tension or something else. I am pretty stuck
 
Physics news on Phys.org
If it is indeed floating then its density is less than water.

It may be light enough and hydrophobic to not exceed the surface tension that also causes the motion due to variations in the force potentials between the water and the ink - electrostatic is the obvious one.
 
Brownian motion might also contribute.
 
It could be held up the surface tension of the water. When that happens, the small object on the surface will move back and forth due to slight perturbations of the water surface.
 

Similar threads

  • · Replies 5 ·
Replies
5
Views
17K
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
4K
  • · Replies 16 ·
Replies
16
Views
7K
  • · Replies 13 ·
Replies
13
Views
2K
  • · Replies 12 ·
Replies
12
Views
7K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 4 ·
Replies
4
Views
5K