Continuous plantation of crops in a field makes the soil poor in certain nutrients such as nitrogen, phosphorus, potassium, etc. Plants require nutrients for their proper growth and functioning. When a farmer continues to grow’ crops one after the other, then all nutrients available in the soil reduce and the crop yield decreases automatically.

There are different methods by which nutrients in the soil can be replenished. Fertilizers and manures contain plant nutrients such as nitrogen, phosphorus, potassium. Fertilizer can be added to the soil. It helps in replenishing exhausted soils with rich sources of organic nutrients. Manure is environment friendly and replenishes the soil with organic nutrients. Compost is decomposed organic material. It reintroduces living organisms and nutrients in the soil. It improves soil structure and provides a healthy environment for plant roots.

How many non-square numbers lie between the following pairs of numbers:

(i) 100² and 101² (ii) 90² and 91²

(iii) 1000² and 1001²

Answer:

i) Between 100² and 101²
Here, n=100 ∴  n x2 = 100 x 2 = 200

∴ 200 non-square numbers lie between 100² and 101² .

(ii)  Between 90² and 91²

Here, n=90  ∴  2 x n = 2 x 90 or 180

∴  180 non-square numbers lie between 90 and 91.

(iii)  Between 1000² and 1001²

Here, n = 1000         ∴  2 x n = 2 x 1000 or 2000
∴  2000 non-square lie between 1000² and 10012.

an infantryman's light gun with a long barrel, typically smooth-bored and fired from the shoulder.

Given, Total number participants = 63
Total prize money distributed =
Rs 3000Winner gets a prize of Rs 100
Who does not win gets a prize of Rs 25
Number of winners = ?
Let the number of winners = m
Since,Number of winners + Number of losers = Total number of participants
Or, m + Number of losers = 63
By transposing ‘m’ to RHS, we getNumber of losers = 63 – m
Now,Total Prize money distributed to winners=
Number of winners X prize money distributed to each winner = m X 100 = 100m
Total prize money distributed to losers
= Number of losers X prize money distributed to each loser= (63 – m) X 25 = (63 x 25) – 25 m = 1575 – 25 m
Now,Total Prize money of winners + Total Prize money of losers =
Total prize money
By substituting the total prize money distributed to winners and total prize money distributed to losers, we get100 m + 1575 – 25 m = 3000
⇒ 100 m – 25 m + 1575 = 3000By transposing 1575 to RHS, we get100 m – 25 m = 3000 – 1575⇒75 m = 1425
After dividing both sides by 75, we get the answer.

Thus, number of winners = 19 Answer

Let the number of winners =x
 

∴  Number of participants who are not winners = (63 - x)
 

∴  Prize money given to:                Winners = xRs 100 = Rs 100 x

                 Non-winner participants = Rs 25  (63-x)

                                                = Rs 25 63 - Rs 25x

                                                 = Rs 1575 - Rs 25x

According to the condition, we have

                                100x + 1575 - 25x = 3000

or                                          75x = 3000 - 1575       [Transposing 1575 to RHS]

or                                           75x = 1425

or                                              x = 1425 75 = 19

    Thus, the number of winners = 19

• The area of the edge of a knife’s blade is extremely small. This creates a pressure high enough for the blade to cut through a material.
• Syringes are used to take blood for blood tests. The pressure of the liquid (blood) forces the liquid to move into the syringe when its plunger is withdrawn.
• When air is sucked out of a drinking straw, the air pressure inside if decreases and the atmospheric pressure outside forces the liquid to go inside the straw.
• Skis have a large area to reduce the pressure on the snow. This ensures that the skis do not sink into the snow too far.
• The pressure under the studs on the soles of football shoes is high enough for them to sink into the ground, which gives extra grip.
• A vacuum cleaner has a fan inside that creates a low pressure inside the device. Consequently, air and dirt particles are sucked into the device.

Manometers

A manometer is a tube-like device which measures atmospheric measure. There are two types: closed tube and open tube, but both measure pressure by comparing the pressure exerted by the atmosphere at one end of the tube with a known pressure at the other. Manometer tubes are typically filled with mercury.

Barometer

Barometers also measure atmospheric pressure. Mercury barometers are a type of closed-tube manometer, while aneroid barometers use a small, spring balance to take the measurement. In the past, mercury barometers were common in family homes where people used them to predict the weather based on the air pressure reading. Rising air pressure meant good weather was on the way, while falling pressure might bring rain.

Find selling price (SP) if a profit of 5% is made on

(a) a cycle of Rs 700 with Rs 50 as overhead charges.

(b) a lawn mower bought at Rs 1150 with Rs 50 as transportation charges.

(c) a fan bought for Rs 560 and expenses of Rs 40 made on its repairs.

Magnetic Force is a force that attracts certain metal objects (like iron and iron filings) towards a magnet.

Electrostatic force is the force exerted by a charged body on another charged or uncharged body. Eg: Take a comb and brush it on a hair 3-4 times and then take it near some small bits of paper. Donot touch the comb with the paper. The bits of paper would get attracted to the comb. This is because the comb is charged because of the rubbing on your hair and it attracts uncharged objects like paper.

Gravitational force is a force exerted by the earth on all objects on it. When a ball is thrown up, it falls to the ground because of gravitational force. The water from a tap always flows downwards because of gravitational force.

The net force is defined as is the sum of all the forces acting on an object. Net force can accelerate a mass. Some or the other force acts on anybody either at rest or motion. The net force is a term used in a system when there is a significant number of forces.  

If N is the number of forces acting on a body, the net force formula is given by,

FNet = F1 + F2 + F3….+ FN

Where,

F1, F2, F3….FN is the forces acting on a body.

British preserved official documents, because they thought that by keeping all the records in written it would be easier for them or any other persons to know about the decisions taken in the past. they clearly noted down all the policies, instructions, plans, agreement and important things related to the administration of the country,  so that in the future, those records can serve as proofs of all the decisions that they had taken. One can study the notes and reports that were prepared in the past.

Mass

1. Refers to the quantity of matter in an object.
2. Mass is independent of gravity.
3. It is the result of comparison of an unknown mass with a known mass called standard mass.
4. Mass is an extensive property. The fundamental unit of mass in the metric system is gram.
5. It is measured in kg in SI units.
6. Mass resists motion.
7. It is a scalar quantity.
8. It is measured with the help of physical balance

Weight
1. Is the force of gravity on an object. Weight = Mass X Acceleration due to gravity
2. Weight is dependent of gravity.
3. Gravity is not constant throughout the earth. So weight may vary from one place to the other.
4. When gravity is constant, mass is directly proportional to weight.
     Mass α weight, when gravity is constant.
5. It is measured in newton in SI units.
6. Weight produces motion. 
7. It is a vector quantity.
8. It is measured  by using a spring balance

Utility is what makes an object or substance a resource.

The factors that determine the utility of any natural resources foremost are ‘human beings’ because only they have the ability to recognise any substances as resources, followed by ‘time’ and ‘technology’ which transform a substance into a resource. Finally, the ‘value’ provides the economical worth of a substance and converts it into a resource.

For example: Uranium found in Ladakh. It was primarily discovered by people, with time technology will be used to utilise it and then its economical value will finally transform it into a resource.

• Soda-acid fire extinguishers contain sodium bicarbonate and sulphuric acid.
• It is the most effective house-hold fire extinguisher.
• It consists of a strong iron vessel with a side discharge nozzle. The iron vessel is filled with sodium bicarbonate solution.
• A small glass bottle, filled with sulphuric acid is supported inside the iron vessel. A knob is fixed just above this bottle.
• On striking the knob, the acid bottle breaks open into the sodium bicarbonate solution. The sulphuric acid reacts with sodium bicarbonate to form sodium sulphate, water and carbon dioxide.