Why camphor moves in water

The stronger pull exerted by the uncontaminated portion of water brings about a movement of the surface and the camphor particles are carried along with it. When after sometime the whole surface settles for the reduced tension, the movement of the camphor too short.

Join The Discussion. Latent heat B. Nuclear fusion C. Refractive index D. Stock value. View Answer. Radiocarbon is produced in the atmosphere as a result of A. Collision between fast neutrons and nitrogen nuclei present in the atmosphere. Action of ultraviolet light from the sun on atmospheric oxygen. Lightning discharge in atmosphere. It is easier to roll a stone up a sloping road than to lift it vertical upwards because A.

Work done in rolling is more than in lifting. Work done in lifting the stone is equal to rolling it. Work done in both is same but the rate of doing work is less in rolling. Work done in rolling a stone is less than in lifting it. Therefore, the water surface tension in between the wings was lower green line than close to the chamber boundaries red line. Direct measurement with a platinum wire diameter 0. If the diameter of the central chamber is large, then the gate can open wide enough to pass the camphor disk cf.

After opening, the disk spontaneously moved toward the left part of the channel, where the surface concentration of camphor was low. When the disk passed to the other side of the gate, the surface concentration of camphor in the left side of the gate became high. On the other hand, the surface concentration inside the gate decreased because of camphor sublimation. As indicated in Fig. Now the wings were pushed towards each other and mechanically closed the gate.

The wings remained closed any time the camphor disk appeared on the left side. The disk motion in the direction from left to right was blocked. The opening of the wings, measured as the distance between the black dots marking the wing opening ends, as a function of the distance between the camphor disk and the midpoint between the dots is shown in Fig.

The black dots were placed a bit away from the opening ends and the distance between them was 7 mm when the gate was closed. We performed a number of experiments with the gate illustrated in Fig. If the disks were placed in the B region cf. If they were initially placed in the A region, then the gate opened just after the first disk got close to the wings, and the disks moved to the B region.

If there were disks in both A and B regions, then a disk from the A region could open the gate and the transition against the diode direction could occur. However, after some time all disks grouped in the B region. An example of such evolution is attached as Movie si1. We adopt the Neumann boundary conditions for eqn 1 at the periphery of the water surface in a sufficiently long rectangular channel and a circular chamber. Initially, a camphor disk is located near one end of the rectangular chamber, so that the camphor disk starts to move to the gate.

In order to avoid collisions between a wing and the chamber boundary, between the wings, or between the camphor disk and a wing, we detect the possible overlap and set normal velocities to zero. The configuration used in the simulation is depicted in Fig. We found that the camphor disk passes through in one direction, but it does not pass in the opposite one. The simulated time evolution of the gate is attached as a Movie si2. The qualitative agreement between experiments and simulations is illustrated in Fig.

It shows superimposed locations of the disk centre D and marks at the opening ends of wings W1 and W2. The time corresponding to a given disk—wing configuration is the value of the z -variable and it is indicated as a coloured point, from red to blue. We can expect that similar models can be used to simulate other systems in which dynamical coupling between the motion of the camphor disks and the geometry of the boundaries is governed by the surface camphor concentration.

We focused our attention on a gate with swinging wings that allow for unidirectional motion of camphor disks. Experiments have shown that the system illustrated in Fig. The camphor disk was always transmitted in the expected direction. In most experiments the disk passed through the gate a few seconds after it was placed on the water surface. Neither in experiments nor in simulations have we observed disk propagation in the reverse direction.

Therefore, it is natural to consider the gate as a chemo-mechanical signal diode for information coded in the presence or absence of camphor disks on the water surface. This result adds to the other applications of surface phenomena for information processing. The gate opens easily if a disk can come to the region in between the wings, so the surface camphor concentration increases and the wings are pushed away. This idea was used to shape the wings from the transmission side of the diode.

On the other hand, the wings should close tightly to prevent the increase of camphor concentration between them if a disk approaches the gate from the blocking side. We have also investigated gates with a single wing that can be pushed towards the channel side by a camphor disk. The experiments have shown that such gates were not reliable.

Therefore, we think that the construction composed of two wings is the most appropriate for other applications. The gate forcing unidirectional motion of camphor disks can be incorporated into more complex devices to obtain the required motion of objects. For example, in a ring-shaped water channel a camphor disk can rotate clockwise or anticlockwise. The blue plastic sheets shaped the channel and the chamber with the gate.

The inner radius of the ring channel was 20 mm, the outer one was 40 mm and thus the width of the ring channel was 20 mm. The chamber where the gate was located was formed by two half-disks with a radius of 20 mm. As seen in Fig. Like in Fig. In experiments unidirectional rotations of the disk were observed in such systems. A sequence of three consecutive rotations before the disk is trapped between the wings and system boundary is illustrated in Movie, si3.

The gate can be used to compose networks showing a complex behaviour of camphor particles. It is known 3,6—8 that the character of the camphor motion depends on the geometry of the water chamber. Let us assume that a few water chambers forcing different types of motion are connected with channels and gates working as diodes. An example is given in Fig. The considered chambers split into two channels at one of their ends, as illustrated in Fig. It can be expected that at the junction a camphor disk randomly selects the channel it moves into.

If the disk enters the channel with a diode then it passes to another chamber. If it enters the channel without the diode, then after reaching the channel end the disk propagates back towards the other end of the chamber.

Assume that we measure the y -coordinate of the disk position and that initially a camphor disk is in chamber 1 of the illustrated system. In the beginning we can expect a few large-amplitude oscillations, followed by some small-amplitude oscillations when the disk stays in chamber 2 and mid-amplitude oscillations when the disk moves to chamber 3. Next large-amplitude oscillations re-appear and the sequence repeats with random transitions between oscillation types mentioned above.

We think that designing a system with such complex motion of the camphor disk without the use of diodes would be very difficult. DOI: Received 16th May , Accepted 26th June Abstract We study the motion of a camphor disk on the water surface in a system with flexible boundaries. Grey and red plastic sheets recline on the water surface.