A student has difficulty in reading the blackboard while sitting in the last row. What could be the defect the child is suffering from? How could is it be corrected?

A 14 years old boy cannot read question written on the black-board lying 5 m away from him. Show with the help of a labelled diagram as to how this defect can be corrected.

A person can not see clearly objects beyond a distance of 1.2 m.Name the defect of vision he is suffering from.What would be the power of correcting lens used to restore proper vision?

What is Accomodation of eye? Write various defects of vision and their cause. How the eye of person suffering from nearsightedness and farsightedness may be corrected ?

A trolley of mass 200 kg moves with a uniform speed of 36 km//h on a frictionless track. A child of mass 20 kg runs on the trolley from one end to the other (10 m away) with a speed of 4 m s^-1 relative to the trolley in a direction opposite to the its motion, and jumps out of the trolley. What is the final speed of the trolley ? How much has the trolley moved from the time the child begins to run ?

While studying pollution of water, a group of students observed mortality of fish in the river flowing through the city and also in the pond which was away from the city but was adjacent to the crop fields. They further found that drains of the city discharged sewage into the river and the water from farms flowed into the pond. Explain how these could be the cause of fish mortality.

Read the following passage and answer the questions. Adsorption is surface phenomenon and its differ from absorption, Which occurs throughout the body of the substance which abosorbs. In physisorption, the attractive forces are mainly van der waals forces while in chemisorption actual bonding occuars between the particles of absorbent and absorbate. Generelly, easily liquifying gases are absorved more easily on the surface of a solid as compared to the gases which are liquified with difficulty. Adsorption increases with the increase in pressure and decreases as the temparature is increased. What is the effect of pressure on the extent of adsorption ?

In an examination hall, there are four rows of chairs. Each row has 8 chairs one behind the other. There are two classes sitting for the examination with 16 students in each class. It is desired that in each row, all students belong to the same class and that no two adjacent rows are allotted to the same class. In how many ways can these 32 students be seated?

A secondary cell after long use has an emf of 1.9 V and a large internal resistance of 380 Omega . What maximum current can be drawn from the cell? Could the cell drive the starting motor of a car?