If you jerk a piece of paper under a book quick enough, the book will not move. Why?

Shyam bought 5 two hundred page notebooks and 3 hundred page notebooks from the school store. The price. of a two hundred page book is 9 rupees and the price of a hundred page book is 4 rupees. How much did Shyam spent? Use any letters you like for the number of two hundred page note books bought from this store, the number of hundred page books bought and the total amount of money spent by a student, and write the relation connecting them.

Stability of a crystal is reflected in the magnitude of its melting points'. Comment. Collect melting points of solid, water, ethyl alcohol, diethyl ether and methane from a data book. What can you say about the intermolecular forces between these molecules?

Write the converse of the following statements. (i) If a number n is even, then n^(2) is even. (ii) If you do all the exercises in the book, you get an A grade in the class. (iii) If two inegers a and b are such that agtb , then a-b is alwàys a positive integer.

A student is doing an experiment in the laboratory using sodium. Suddenly, a piece of sodium falls into liquid ammonia. (a) What changes can you observe in liquid ammonia? (b) What is the reason for the change? (c) If the solution is kept for a long time it is changed into bronze colour. Why?