Every surface of a liquid has a surface tension that tends to make the surface of it to a minimum. This is because all the atoms on the surface has a higher energy than those found on the inside.
Suppose a drop on a solid surface, this problem has been addressed and raises the following solution:
When sufficiently inclined plane on which the drop is located , it begins to slip and wetting angle (A) changes differently depending on whether the front or rear of the drop. This phenomenon is called hysteresis wet.
Suppose that somehow forces the lower surface of the drop remains contact motionless with respect to the solid surface, tilting the drop is a shift viscous fluid over the blades tend to deform the surface.
Source: Wikipedia
deformation continues until the surface of the drop has accumulated such a strain that is able to counteract the force of gravity. Original angles have changed to their new values, which are typical of a phenomenon of wetting hysteresis. Suppose now that the base is released from the drop of his bond with the surface.
MOVEMENT The drag
molecules near the base acquire a tangential velocity whose magnitude depends on the interactions between the two surfaces. If there are no viscous forces of any kind between the two surfaces will drop its original form as you go down, otherwise the hysteresis decrease in function persists even as the viscosity falls between surfaces. The energy dissipated by viscosity is equal to the gravitational potential energy lost. This form of motion is called drag and drop features because all the moves as a block:
Experimentally this movement Brownian particle can be determined by placing the entire volume of the drop and record the net movement in each area of \u200b\u200bthe drop.
TRACK MOVEMENT
Based on the motion previous block, if the drop retains its hysteresis balance of forces on particles from the ends of the interface is broken. Cos (A) is now higher than it is for the balance and the particle is at the end of the base experiences a net force that tends to drag down the slope, with greater force than that experienced by particles in through the interface. The leading particle thus advance faster than those located in the middle of the interface forming a "gap", that space will be filled by other particles that are in the environment, these particles come from the surface of the drop as it is here where the most unstable particles. In the rear the last particle is out of balance, since the number of particles in the interface can not grow indefinitely or lower surface of the drop indefinitely, the particles out of equilibrium in the rear leave the interface to move towards the surface. The resulting motion is typical for a tank track, can be illustrated by the following image:
MOVEMENT The drag
molecules near the base acquire a tangential velocity whose magnitude depends on the interactions between the two surfaces. If there are no viscous forces of any kind between the two surfaces will drop its original form as you go down, otherwise the hysteresis decrease in function persists even as the viscosity falls between surfaces. The energy dissipated by viscosity is equal to the gravitational potential energy lost. This form of motion is called drag and drop features because all the moves as a block:
Experimentally this movement Brownian particle can be determined by placing the entire volume of the drop and record the net movement in each area of \u200b\u200bthe drop.
TRACK MOVEMENT
Based on the motion previous block, if the drop retains its hysteresis balance of forces on particles from the ends of the interface is broken. Cos (A) is now higher than it is for the balance and the particle is at the end of the base experiences a net force that tends to drag down the slope, with greater force than that experienced by particles in through the interface. The leading particle thus advance faster than those located in the middle of the interface forming a "gap", that space will be filled by other particles that are in the environment, these particles come from the surface of the drop as it is here where the most unstable particles. In the rear the last particle is out of balance, since the number of particles in the interface can not grow indefinitely or lower surface of the drop indefinitely, the particles out of equilibrium in the rear leave the interface to move towards the surface. The resulting motion is typical for a tank track, can be illustrated by the following image:
Experimentally this movement could be seen placing Brownian particles near the surface and recording the movement, recording the spread of ink etc.
global movement of the drop will be a combination of both movements.
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