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# factors affecting surface tension

Question:A particular rod shaped object has a higher density than water. The object is such that it is normally WETTED by water. Is it possible to float the object on the surface of water (manipulating surface tension)? we all know that denser object can float. But the question is: whether any other condition attributed on the nature of the object and liquid(such as 1. shape 2. contact area 3.chemical property)?

Answers:The paper-clip example is interesting: It shows that even a metal object can be supported against gravity if the surface tension is important enough. In this case, it IS important, because of the following factors: - the force of the surface tension is proportional to the surface of exposure (contact area) of the metal to the water. In the case of a paper clip, this is 2 times the length of the paper clip. - the force of gravity is proportional to the mass. The mass of the paper clip is small, because it is so thin (the wire, that is). - the water does NOT wet the metal of the paper clip: so the water tries to reject the metal. The first two factors mean that the surface tension can be significant for this little paper clip: If the wire were thicker, it wouldn't work. The second factor means that, when you look sideways at the floating paper clip, you will see that the water attaches to the metal of the paper clip at a downward slope: as you move away from the metal, the water level goes up, because the water is rejecting the metal. But that means that when the water does contact the metal, the pull of the surface tension will follow the direction of the water level and pull it UP: that is why the surface tension LIFTS the paper clip. However, your question asks whether this will work if the material is WETTED by water. The answer is, No. If the material is wetted by water, that means water will NOT REJECT it, and the water level will be sloping down away from the material. That means that the surface tension will be pulling DOWNWARD.

Question:

Answers:1. Cohesion: is the sticking together of similar molecules. Water is very cohesive. This allows water to be pulled along a pathway with relative ease. 2. Surface Tension: cohesion allows water to pull together and form droplets or form an interface between it and other surfaces. The measure of how hard it is to break this interface is its surface tension. Water allows materials to rest upon it if the surface tension is not broken. Pollen, dust, water insects, and other biological materials are able to remain on the surface of the water because of this tension. 3. Adhesion: The sticking of one substance to another. Water is a good adhesive. It will cling on to many objects and act as a glue. Capillary Action is an example of cohesion and adhesion working together to move water up a thin tube as in the xylem of plants.

Question:Identify the major factor affecting reaction rates that accounts for the following abservations: 1. tadpoles grow more rapidly near the cooling water discharge from a power plant. 2. enzymes accelerate certain biochemical reactions, but are not consummed. 3. Campfires are started with twings rather than logs for wood. 4. Iron and steel corrode more rapidly near the coast of an ocean than in the desert. please help!

Answers:1. increased temperature 2. catalyst 3. increased surface area 4. presence of moisture, or salt (catalyst).

Question:2. what is one way you could reduce the friction between two surfaces? 3. the acceleration due to gravity of all objects in free fall is the same. why, then, do some objects fall through the air at a different rate? 4. how dose mass differ from weight ? 5. what is the law of universal gravitaion?

Answers:1.The 2 factors on which friction two body is depended upon > The mass of the body, >the coefficient of Static or limiting or dynamic friction( as the case may be) 2.By adding any lubricating agent like grease, or oil. 3. If u c the defination of acc. due to gravity it says When a body of mass 1kg undergoes a free fall it acquires an acceleration of 9.8 m/s^2 due to the gravity( not considering the air resistance) So bodies with different mass fall with different acceleration. Moreover if u consider the air resistance, the acceleration of a body with more surface area(which has more air resistance) is lessened. 4.Wt is a force( of the gravity) We know, Force = mass * acceleration So here on earth a=g ( acc. due to gravity) which is equal to 9.8m/s^2 Wt. = mass * 9.8 ( under the effect of earth's gravitation only); Thus wt= mass * g ( acceleration caused due to the gravitation of any body) Thus wt. is directly proportional to mass of the body in a particular place. 5. Law of universal gravitation states that there is a force between any two in this universe which is not depended on the material between them. thus f = (G*m1*m2)/ r^2 ===> G = (f * r^2)/ m1*m2 here f -------> force between the two body( which is g for the earth) G------> Universal gravitation constant m1 & m2--> mass of the two bodies r= distance between the two bodies.