CBSE ADDA

Science Sample Paper -2015 Section A 1. If the equation kx2+ 4x+ k=0 has two equal roots, then (a) k = ±2 (b) k = 0 (c) k = 2 (d) none of these 2. If the sum of n terms of an A.P., is 2n2 +4n, then its nth term is (a) 4n + 2 (b) 4n + 5 (c) 10n - 4 (d) none of these 3. If tangents TA and TB from a point T to a circle with center O are inclined to each other at an angle of 70° then <TOA is equal to (a)80° (b) 70° (c) 55° (d) 50° 4. To divide a line segment AB in the ratio 5:3, first a ray AX is drawn so that < BAX is an acute angle and then at equal distances points are marked on the ray AX such that the minimum number of these points is (a) 12 (b) 11 (c) 10 (d) 8 5. If the circumference and area of a circle are numerically equal, then diameter of the circle is  (a)2x (b) 2 (c) 4 (d) 4x 6. The number of solid spheres, each of diameter 2 cm that could be moulded to form a solid metal cylinder of height 45 cm and diameter 4 cm is (a)14 (b) 15 (c) 135 (d)

Gist of Lesson for Quick Revision (By JSUNIL) 1. Periodic table: The table which classifies all the known elements on the basis of their properties in such a way that elements with similar properties are grouped together. The first classification of elements was as metals and non-metals.  In 1789, Lavoisier first attempted to classify the elements into two divisions namely Metals and Non-metals This served only limited purpose mainly because of two reasons:  (i). All the elements were grouped in to these two classes only. The group containing metals was very big.  (ii)  Some elements showed properties of both-metals and non-metals and they could not be placed in any of the two classes. 2. All earlier attempts on the classification of the elements were based on their atomic weights. 3. The first attempt towards the classification of elements was made by Johann Dobereiner, a German chemist in 1829. He made sets of three elements which showed similar chemical p

Trend Setter Basic Science Publication - Bharati Bhawan Solutions Very Short Answer type Questions A1.Is light year a unit of time or distance? Define `1 light year? Ans: Light year is a unit of distance .one light year is a distance covered by light in 1 year. A2.What is the source of stars energy? Ans: The source of stars energy is nuclear fusion in which hydrogen atoms split up into helium atoms and large amount of energy is librated. A3.What gives galaxies different shapes? Name a few common shapes of galaxies. Ans: The  arrangement  of stars gives galaxies different shapes of galaxies. About 100 billians galaxies in the universe some of them are in shape of spiral, ring like or elliptical. A4.What is the big Dipper? Ans: The seven brightest stars in between the month of February and may form a shape of dipper in northern sky. This constellation  is called Big deeper or Saptarshi. A5. Why are Mercury venues, and Mars called terrestrial planets? Ans: This is because t