Answer briefly:
(a) Why are villi present in the intestine and not in the stomach?
(b) How does pepsinogen change into its active form?
(c) What are the basic layers of the wall of alimentary canal?
(d) How does bile help in the digestion of fats?

How does bile help in digestion of fat ?

Answer briefly : (a) How do you perceive the colour of an object ? (b) Which part of our body helps us in maintaining the body balance ? (c) How does the eye regulate the amount of light that falls on the retina.

A player throws a ball upwards with an initial speed of 29.4 ms^(-1) (a) What is the direction of acceleration during the upward motion of the ball ? (b) What are the velocity and acceleration of the ball at the highest point of its motion ? (c) Choose the x = 0 m and t=0 s to be the location and time of the ball at its highest point vertically downward direction to be the positive direction of x-axis and give the signs of position, velocity and acceleration of the ball during its upward and downward motion. (d) To what height does the ball rise and after how long does the ball return to the player's hands ? (Take g = 9.8 ms^(-2) and neglect air resistance).

Correct the wrong statements among the following : (a) In earthworm, a single male genital pore is present. (b) Setae help in locomotion of earthworm. (c) Muscular layer in the body wall of earthworm is made up of only circular muscles. (d) Typhlosole is the part of intestine of earthworm.

In an experiment to estimate the size of a molecule of oleic acid 1 mL of oleic acid is dissolved in 19 ml of alcohol. Then I mL of this solution is diluted to 20 mL by adding alcohol. Now 1 drop of this diluted solution is placed on water in a shallow through. The solution spreads over the surface of water forming one molecule thick layer. Now lycopodium powder is sprinkled evenly over the film and its diameter is measured. Knowing the volume of the drop and area of the film we can calculate the thickness of the film which will give us the size of oleic acid molecule. Read the passage carefully and answer the following questions. (a) Why do we dissolve oleic acid in alcohol ? (b) What is the role of lycopodium powder ? (c) What would be the volume of oleic acid in each ml of solution prepared ? (d) How will you calculate the volume of n drops of this solution of oleic acid ? (e) What will be the volume of oleic acid in one drop of this solution ?

(a) Magnetic field lines show the direction (at every point) along which a small magnetised needle aligns at the point). Do the magnetic field lines also represent the lines of force on a moving charged particle at every point? (b) Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why? (c) If magnetic monopoles existed, how would the Gauss's law of magnetism be modified? (d) Does a bar magnet exert a torque on itsell due to its own field? Does one element of a current-carrying wire exert a force on another element of the same wtre? (e) Magnetic field arises due to charges in motion. Can a system have magnetic moments even though its net charge is zero?

Two charges –q and +q are located at points (0, 0, –a) and (0, 0, a), respectively. (a) What is the electrostatic potential at the points (0, 0, z) and (x, y, 0) ? (b) Obtain the dependence of potential on the distance r of a point from the origin when r//a gt gt 1 . (c) How much work is done in moving a small test charge from the point (5,0,0) to (–7,0,0) along the x-axis? Does the answer change if the path of the test charge between the same points is not along the x-axis?