Calculation of the weight of an insect floating by surface tension

In summary: From this, you can calculate the tension in the surface (the force acting on one leg), by multiplying the surface tension by the length of the (arc of the) leg at the surfaceMoreover, this force is not acting vertically, so you need to take components into account.In summary, the surface tension of 0.1 N/m acting on the length 20.1 × 10^-5m (corresponding to the half-submerged leg ends with radius 3.2 × 10^-5m) results in a force of 1 × 10^-5N acting on one leg. Taking into account the angle of the footfall, the force on one leg becomes 5 × 10^-6
  • #1
srm
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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?
 
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  • #2
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 ?
 

What is the surface tension of water?

The surface tension of water is the measure of the force that holds the molecules of water together on the surface. This force is what allows insects to float on the surface of water.

How is the weight of an insect calculated using surface tension?

The weight of an insect can be calculated by measuring the surface area of the insect that is in contact with the water and multiplying that by the surface tension of water. This calculation takes into account the force that the insect exerts on the water to stay afloat.

What is the importance of calculating the weight of an insect using surface tension?

Calculating the weight of an insect using surface tension is important because it allows scientists to study the behavior and adaptations of insects that are able to float on the surface of water. It can also provide insights into the properties of surface tension and the effects of surface tension on small organisms.

Are there any limitations to using surface tension to calculate the weight of an insect?

Yes, there are some limitations to using surface tension to calculate the weight of an insect. It only takes into account the force that the insect exerts on the water and does not consider other factors such as the weight of the insect's body or the effects of wind or other external forces.

Can the weight of an insect calculated using surface tension be used for other purposes?

Yes, the weight of an insect calculated using surface tension can also be used for other purposes such as studying the effects of pollutants on the surface tension of water or developing new materials that mimic the surface tension of water for various applications.

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