List three categories of substances which are ensured greater diffusion due to large surface/volume ratio of the cells.

The surface-to-volume ratio of a cell

List any three special abilities of humans which have evolved due to large-sized brain.

Now when the surface is smooth , the toy car travels larger distance. It is found that friction is caused by interlocking of irregularities on the two surfaces in contact . Irregularities between two surfaces in contact. The above figure shows minute irregularities on two surfaces which are locked into one another . If we want to move any surface , some part of the external force applied is used to overcome this interlocking want to maove any surface , some part of the external force applied is used to overcome this interlocking . A rough surface has a large number of irregularities , so the force of friction is greater . A smooth surface has small number of irregularities , so the force of friction is less. 2. Normal reaction : The force of friction depends on the normal reaction also. As the normal reaction increases , the interlocking between two surfaces in contact increases as they press harder against each other and hence friction increases .

Comparing small and large cells, which statement is correct ? (1) Small cells have a small surface area per cells (2) Exchange rate of nutrients is fast with large cells (3) Small cells have a large surface area per volume ratio (4) Exchange rate of nutrients is slow with small cells

A mixture of SO_(2) and O_(2) in the molar ratio 16:1 is diffused through a pin hole for successive effusion three times to give a molar ratio 1:1 of diffused mixture. Which one are not correct if diffusion is made at same P and T in each operation? ( I ) Eight operation are needed to get 1:1 molar ratio. ( II ) Rate of diffusion for SO_(2):O_(3) after eight operations in 0.707 . ( III ) Six operations are needed to get 2:1 molar ratio for SO_(2) and O_(2) in diffusion mixture. ( IV ) Rate of diffusion for SO_(2) and O_(2) after six operations is 2.41 .

In order to get maximum calorific output a burner should have an optimum fuel to oxygen ratio which corresponds to three times as much oxygen as is required theorectically for complete combusion of the fuel A burner which has been adjused for methane as fuel (with x L h^(-1) of CH_(4) and 6x Lh^(-1) of CO_(2)) is to be readjusted for butane C_(4)H_(10) in order to get the same calorific output what should be the rate of supply to butane and oxygen? Assume that losses due to incomplete combustion etc are the same for both fuels and that the gases behave ideally Heats of combusion CH_(4) =809 kJ mol^(-1),C_(4)H_(10) =2878 kJmol^(-1) .

In order to get maximum calorific output a burner should have an optimum fuel to oxygen ratio which corresponds to three times as much oxygen as is required theorectically for complete combusion of the fuel A burner which has been adjused for methane as fuel (with x L h^(-1) of CH_(4) and 6x Lh^(-1) of CO_(2)) is to be readjusted for butane C_(4)H_(10) in order to get the same calorific output what should be the rate of supply to butane and oxygen? Assume that losses due to incomplete combustion etc are the same for both fuels and that the gases behave ideally Heats of combusion CH_(4) =809 kJ mol^(-1),C_(4)H_(10) =2878 kJmol^(-1) .

The force of interaction between the molecules of same substance is called cohesive force hile force of interaction between molecules of different substances is called adhesive force . Both the forces are attracive and have a range of about 10 A . If we consider a molecule . A well inside a liquid we find that it is equally attracted by the surrounding molecules in all the directions ( with a sphere of radius 10 Å ) and so it does not experience any resultant force . On or near the surface of a liquid , the molecules do not exist on the free side and so a molecule ( say B ) experiences a resultant force vertically downwards into the liquid . For this reason , the molecules of the surface have a tendency to go into the liquid . Thus , the surface tends to contract and gives rise to surface tension . As surface molecules like B experience a net downward force of cohension and have tendency to go down , so in increasing the area of the surface more molecules are to be shifted to the surface from inside . Thus , more mechnical work will have to be done against the net downward force of cohension . This work is stored by the molecules in the surfaces as potential energy called free surface energy . Furthermore , molcules like P , in contact with the liquid will stick to the solid surface , i.e will meet it if the force of adhesion A is greater than net force of cohension C . The liquid will not the solid surface if C gt A Also , molecules like Q at the surface in contact with the solid will experience a net force of cohension C_(R) . If adhesion A is greater then cohension C_(R) , the resultant force will be F . As the liquid can't support tangential force , F must be perpendicular to the surface of the liquid . So , the menisus will be concave and the angle of contact will be acute ( gt 90^(@)) . However , if adhesion is lesser than cohension , the resultant force F will be directed into the liquid and so the menisus ( which is perpendicular to F as liquid support tangential force ) will be convex and the angle of contact will be obtuse ( gt 90^(@)) A liquid particle B , which is present in the vicinity particle A can exert a force on A if the distance of B from A is

The force of interaction between the molecules of same substance is called cohesive force hile force of interaction between molecules of different substances is called adhesive force . Both the forces are attracive and have a range of about 10 A . If we consider a molecule . A well inside a liquid we find that it is equally attracted by the surrounding molecules in all the dirctions ( with a sphere of radius 10 Å ) and so it does not experience any resultant force . On or near the surface of a liquid , the molecules do not exist on the free side and so a molecule ( say B ) experiences a resultant force vertically downwards into the liquid . For this reason , the molecules of the surface have a tendency to go into the liquid . Thus , the surface tends to contract and gives rise to surface tension . As surface molecules like B experience a net downward force of cohension and have tendency to go down , so in increasing the area of the surface more molecules are to be shifted to the surface from inside . Thus , more mechnical work will have to be done against the net downward force of cohension . This work is stored by the molecules in the surfaces as potential energy called free surface energy . Furthermore , molcules like P , in contact with the liquid will stick to the solid surface , i.e will meet it if the force of adhesion A is greater than net force of cohension C . The liquid will not the solid surface if C gt A Also , molecules like Q at the surface in contact with the solid will experience a net force of cohension C_(R) . If adhesion A is greater then cohension C_(R) , the resultant force will be F . As the liquid can't support tangential force , F must be perpendicular to the surface of the liquid . So , the menisus will be concave and the angle of contact will be acute ( gt 90^(@)) . However , if adhesion is lesser than cohension , the resultant force F will be directed into the liquid and so the menisus ( which is perpendicular to F as liquid support tangential force ) will be convex and the angle of contact will be obtuse ( gt 90^(@)) The free suface energy , stored in the surface is because of work done

A conducting bolloon of the radius a is charged to potential V_(0) and held at a large height above the earth ensures that charge distribution on the surface of the balloon remains unaffected by the presence of the earth. It is connected to the earth through a resistance R and a value in the balloon is opened . The gas inside the balloon escapes from value and the size of the balloon decreases. The rate of decrease in radius of the balloon is controlled in such a manner that potential of the balloon remains constant. Assume the electric permittivity of the surrounding air equals to that of free space (epsilon_(0)) and charge cannot leak to the surrounding air. The rate at which radius r of the balloon changes with time is best represented by the equation