Surface energy theoretical questions work shown

[johnq2k7]

1.) When woven material is dry, air will pass directly through. When immersed in water however, clothing can be used to trap air and provide buoyancy.

a.) With the aid of the diagram, explain why this is so?

need help explaining theoreticallly?


b.) Give an eq. which can be used to calc. the buoyance force (Fb) which can be provided by a vertical cylinder of radius r_c, made from a cloth with a uniform pore size of radius r_p. assume that the cloth is completely wetted with water which has a surface energy y and that the cylinder can be as long as is necessary

need help coming up with an equation here

c.) based on your equation what would be the best type of material and shape for a cloth float?

2.) When a drop of water is placed between two microscope slides they stick together.


a.) with the aid of a diagram showing the shape of the interfaces, explain the force holding them together.

my work: they stick together because the force can be balanced horizontally and vertially, since the pressurs across the lower and upper slides are the same ignoring gravitational effects therefore they stick together... not sure if my explanation is correct?



b.) Will the sheets still stick together if they are immersed in water? Explain

no because of the pressure differences between the surface and water would cause the two slides to separate.. not sure if my explanation is correct..

please help me with these theoretical understanding questions!

 

[anathema]

a.) The diagram shows that when the cloth is dry, the air can easily pass through the pores in the cloth, as the pores are not filled with any liquid. However, when the cloth is immersed in water, the water molecules fill the pores and create a barrier for the air to pass through. This trapped air provides buoyancy to the cloth, allowing it to float on the surface of the water.

b.) The buoyancy force (Fb) can be calculated using the following equation: Fb = (r_c^2-r_p^2)πy, where r_c is the radius of the cylinder, r_p is the radius of the pores, and y is the surface energy of water. This equation takes into account the difference in pressure between the inside and outside of the cylinder, as well as the surface tension of water that holds the cloth pores together.

c.) Based on the equation, the best type of material for a cloth float would be one with a large radius of pores (r_p) and a small radius of the cylinder (r_c). This would maximize the surface area of the pores and therefore the surface tension force, resulting in a higher buoyancy force. The shape of the cloth float should also be cylindrical, as this shape allows for the maximum surface area of the pores to be exposed to the water.

2.) a.) The force holding the two microscope slides together is surface tension. When a drop of water is placed between the two slides, the water molecules at the surface of the drop experience a net inward force due to the cohesive forces between water molecules. This results in a concave shape of the water droplet, which creates a larger surface area for the cohesive forces to act upon, thus holding the two slides together.

b.) The sheets will still stick together if they are immersed in water. This is because the surface tension force is still present, even in water. The water molecules at the surface of the drop will still experience a net inward force, creating a concave shape and holding the two slides together. However, the pressure difference between the inside and outside of the drop may cause the drop to flatten out, but the two slides will still remain stuck together due to the surface tension force.

 

[kerimek]

a.) The diagram shows the surface energy of the cloth and water. When the cloth is dry, the air can easily pass through the pores of the cloth because the surface energy of air is lower than that of the cloth. However, when the cloth is immersed in water, the surface energy of water is higher than that of the cloth. This creates a surface tension at the interface between the cloth and water, causing the water molecules to be pulled towards each other, trapping air in the pores of the cloth and providing buoyancy.

b.) The buoyancy force (Fb) can be calculated using the equation Fb = 2πr_c(r_c + r_p)y, where r_c is the radius of the cylinder, r_p is the pore size of the cloth, and y is the surface energy of water. This equation takes into account the surface tensions at both the top and bottom of the cylinder, and the circumference of the cylinder.

c.) Based on the equation, the best type of material for a cloth float would be one with a high surface energy, as this would create a stronger surface tension and provide more buoyancy. The shape of the cloth float should also be cylindrical, as this allows for the maximum amount of surface area to interact with the water and create surface tension.

a.) The force holding the two microscope slides together is adhesive force. The water molecules on the surface of the slides are attracted to each other due to surface tension, creating a bond between the two slides.

b.) No, the sheets will not stick together if they are immersed in water. This is because the surface tension of water is higher than that of the slides, causing the water molecules to be more strongly attracted to each other than to the slides. This results in the water molecules pulling away from the slides, breaking the adhesive force between them.