Calculation of the weight of an insect floating by surface tension

Click For Summary
SUMMARY

The discussion focuses on calculating the weight of a six-legged insect supported by surface tension. The insect's legs, modeled as spheres with a radius of 3.2 × 10-5 m, distribute its weight equally. The surface tension coefficient is 0.1 N/m, and the angle of footfall is θ = π/3 radians. The calculated force on one leg is 1 × 10-5 N, leading to a total force of 6 × 10-5 N for all legs, resulting in an estimated mass of approximately 6.122 × 10-6 kg, which is slightly higher than the expected mass of 5 × 10-6 kg.

PREREQUISITES
  • Understanding of surface tension and its formula (F = T × L)
  • Knowledge of basic physics concepts such as force and mass
  • Familiarity with trigonometric functions, specifically cosine
  • Ability to perform calculations involving small values and scientific notation
NEXT STEPS
  • Review the principles of surface tension in liquids
  • Study the effects of angle on force distribution in physics
  • Learn about the properties of spheres and their impact on buoyancy
  • Explore common errors in physics calculations involving small masses
USEFUL FOR

Students studying physics, particularly those focusing on fluid mechanics and surface tension, as well as educators seeking examples of practical applications of these concepts.

srm
Messages
1
Reaction score
0

Homework Statement


The surface of a liquid is just able to support the weight of a six-legged insect. The leg ends can be assumed to be spheres each of radius 3.2 × 10−5 m and the weight of the insect is distributed equally over the six legs. The coefficient of surface tension in this case is 0.1 N/m and the angle of the footfall with respect to the vertical is θ = π/3 radians (see figure). The mass of the insect is close to_

Homework Equations


For calculating the surface tension F= T×L where T is the surface tension in F/m and L is the length over which the surface tension works.

The Attempt at a Solution


I assumed that the sphere is floating halfway, so the surface tensions acts on the length 2πR. I calculated 2πR which is 20.1×10-5m. Then I multiplied it with T, and the force turns out to be 2.01×10-5 N. Multiplied it by cosπ/3 and obtained 1×10-5. This must be the force on one leg. So, I multiplied it with 6 and got 6×10-5N. Now if you calculate the mass, it turns out to be about 6.122×10-6. But the answer is 5×10-6.
Where am I going wrong?
 
Physics news on Phys.org
Hello srm, :welcome:

What a nice exercise !

srm said:
I assumed that the sphere is floating halfway
Does that correspond to what you (not me, I don't even see a figure :rolleyes: ) see in the figure ?
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
14K
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 1 ·
Replies
1
Views
3K
Replies
11
Views
3K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 6 ·
Replies
6
Views
7K
Replies
3
Views
4K
Replies
4
Views
5K
  • · Replies 32 ·
2
Replies
32
Views
6K