force physics science questions with pictures

Clinical test for jaundice: Normal urine has a surface tension of about 66 dynes/centimeter but if bile is present (a test for jaundice), it drops to about 55.But if you touch the tent material with your finger, you break the surface tension and the rain will drip through.

Don't touch the tent!: Common tent materials are somewhat rainproof in that the surface tension of water will bridge the pores in the finely woven material.

If the surface is agitated to break up the surface tension, then needle will quickly sink.

Floating a needle: A carefully placed small needle can be made to float on the surface of water even though it is several times as dense as water.

Walking on water: Small insects such as the water strider can walk on water because their weight is not enough to penetrate the surface.

Hydrofuge hairs line the body surface of the water strider.

The legs are strong, but have flexibility that allows the water striders to keep their weight evenly distributed and flow with the water movement. The legs of a water strider are long and slender, allowing the weight of the water strider body to be distributed over a large surface area. Water striders use the high surface tension of water and long, hydrophobic legs to help them stay above water.Water striders use this surface tension to their advantage through their highly adapted legs and distributed weight. Water striders are able to walk on top of water due to a combination of several factors. Sources/Usage: Some content may have restrictions. When an object is on the surface of the fluid, the surface under tension will behave like an elastic membrane. (Source: Woodrow Wilson Foundation).ĭue to the surface tension, small objects will 'float' on the surface of a fluid, as long as the object cannot break through and separate the top layer of water molecules. Thus the surface is under tension, which is probably where the name 'surface tension' came from. This inward net force causes the molecules on the surface to contract and to resist being stretched or broken. However for a molecule on the surface of the liquid, there will be a net inward force since there will be no attractive force acting from above. Within a body of a liquid, a molecule will not experience a net force because the forces by the neighboring molecules all cancel out (diagram). In fact, other than mercury, water has the greatest surface tension of any liquid. This surface layer (held together by surface tension) creates a considerable barrier between the atmosphere and the water. This results in a stronger bond between those molecules that actually do come in contact with one another, and a layer of strongly bonded water (see diagram). At the surface, however, there are fewer water molecules to cling to since there is air above (thus, no water molecules).

Water molecules want to cling to each other. At the surface, though, the outmost layer of molecules, has fewer molecules to cling to, therefore compensates by establishing stronger bonds with its neighbors, this leading to the formation of the surface tension. Surface tension in water owes to the fact that water molecules attract one another, as each molecule forms a bond with the ones in its vicinity. Surface tension could be defined as the property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of the water molecules. Those on the surface have no neighboring molecules above and, thus, exhibit stronger attractive forces upon their nearest neighbors on and below the surface. The cohesive forces between molecules in a liquid are shared with all neighboring molecules. It is not really true that a 'skin' forms on the water surface the stronger cohesion between the water molecules as opposed to the attraction of the water molecules to the air makes it more difficult to move an object through the surface than to move it when it is completely submersed. The molecules at the surface of a glass of water do not have other water molecules on all sides of them and consequently they cohere more strongly to those directly associated with them (in this case, next to and below them, but not above). The cohesive forces between liquid molecules are responsible for the phenomenon known as surface tension. The high surface tension helps the paper clip - with much higher density - float on the water. It seems to defy the laws of physics, but a paper clip made of steel can indeed float on the water surface.

Force physics science questions with pictures