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During sunrise and sunset, the light has to travel a long distance in the atmosphere. So light of small wavelength scatters and the least scattered light reaches our eyes. Red is the least scattered light. So sky looks red.

The following are the reasons for using steel instead of other materials to make robots. 

1. Steel is commonly available and it is found in the form of an alloy of Iron.

2. It is stronger than other metals like aluminum.

3. Welding is easy to do 

4. It blunts tools easily.

Hence the above reasons make steel favorable building material for Robots.


The material selected for making robot depends on the application. Wood, plastics, aluminium, steel, ceramics etc are used to make a robot. 

How many stars in milky way?



1 2 3 4 5 6 7 ?

acc. to series the ans. is 8

3.20 b) Given the resistances of 1 Ω, 2 Ω, 3 Ω, how will be combine them to get an equivalent resistance of (iii) 6 Ω

Attach them in series

4 men and 6 women complete a task in 24 days. If the women are at least half as efficient as the men, but not more efficient than the men, what is the range of the number of days for 6 women and 2 men to complete the same task?

  1. 30 to 33.6 days
  2. 32 to 35 days
  3. 33.6 to 35 days
  4. 30 to 35 days


Question 6. Let ∗ be the binary operation on N given by a ∗ b = L.C.M. of a and b. Find

(v) Which elements of N are invertible for the operation ∗?


Who noticed the deflection of the compass needle every time the current was passed through the wire? When an electric current flows through a wire, it behaves like a magnet.

Hans Christian Oersted was the first person who noticed the deflection of the compass needle every time the current was passed through the wire. When an electric current flows through a wire, it behaves like a magnet.
It can be done by Connecting a large Resistance R in series with the Galvanometer

By connecting a high resistance in series with the galvanometet

what is the difference between the two ?

The prefix poly means many. So the word polynomial refers to one or more than one term in an expression. The relationship between these terms may be sums or differences. You call expression with a single term a monomial, an expression with two terms is a binomial, and expression with three terms is a trinomial. Here we are only discussing Binomial along with their exponents.

HOF is an oxidizing agent which is extremely unstable and it is highly reactive and corrosive in nature. It is used as the explosive material because it is highly unstable due to the high electronegativity difference between fluorine and hydrogen and due to its property of breaking down into HF and O2   

Reaction showing breakdown of HOF 

2 HOF → 2 HF + O2

Jana Gana Mana is our national anthem. Originally it was composed in Bengali as Bharoto Bhagyo Bidhata by Rabindranath Tagore.

pressure inside a liquid jet in excess of atmostpheric pressure . for example if aglass tube of samll diameter is partially immersed in water , the water will wet the surface of the tube ant it will rise in the tube to some height above the normal water surface . In this case, the water surface is concave upward.


What is displacement and distance

Distance:- “how much ground an object has covered” during its motion. It is a scalar quantity.   Displacement:- how far out of place is an object. It is the shortest distance between two points. It is a vector quantity. Example:- If a particle is moving in a circular motion. After the first cycle of its motion, the distance covered by this particle is   (r is the radius of the circle. But the...
  • In this collision (K.E)_{initial} \neq (K.E.)_{final}

  • Coefficient of restitution 0 < e < 1 

  • As (K.E)_{initial} > (K.E.)_{final}

The loss in kinetic energy appears in other forms, such as heat, sound etc. 

Ex- Collision between two billiard balls. All majority of collision belong to this category.

momentum is conserved whereas KE is not conserved as in elastic collision

Intrinsic semiconductors are a pure form of semiconductors. Extrinsic semiconductors are obtained when an impurity is added to an intrinsic semiconductor.

Intrinsic semiconductors are the ones which are semiconductors by nature. For example silicon and Germanium (group 14 elemets). But these elements are conductors  of electricity  at high temperatures and at room temperature they are insulators. Even when we provide high temperature they are poorly conducting ie they conduct but it is not enough. so In order to improve their conductivity we Dope...
If not then the loss in kinetic energy is transferred into which form of energy??



Which of the species is more stable O or N? Nitrogen is more stable than Oxygen due to half-filled electrons in Nitrogen.

Both are active, but O is more active w.r.t. N due to its high electronegativity[ En(O) = 3.5 & En(N) = 3.0 ]. Hence, N is more stable w.r.t. O

A massless rope is fixed at one end as shown in fig. Two boys of masses 40kg and 60kg are moving along the rope. The former climbing up with an accelaration of 2m/s^2 while  later coming down with constant velocity of 5m/s. The tension at fixed support will be (g=10m/s^2)