Water fountains work due to the pressure exerted by water on the walls of the fountain pipe. It further depends on the force by which water enters the pipe.

Porters place a round piece of cloth on their heads to increase the area of contact of the load with their head. So the pressure on their head is reduced and they can carry heavy load easily.

Substances that burn with flame are candle, oil lamp.
Substances that burn without flame are coal, charcoal.

Frictional force always act in the direction opposite to the direction of motion, so it will act towards west.

When the two forces acts in same direction, the net force is the sum of both the forces.

Due to insufficient availability of oxygen in room, keeping angithi in the closed room is not preferred as carbon monoxide gas is produced which can kill persons sleeping in that room.

CNG is a good alternative to petrol and diesel in vehicles because it is a clean fuel and does not cause air pollution. It is filled in cylinders.

Seed drill is an odd pair in the above given set of tools as it is a modern agricultural tool used to sow seeds at uniform distances and to properly cover them with soil.

Since the rolling friction is smaller than the sliding friction and sliding is replaced in most machines by rolling with the use of ball bearings. Common examples are the use of ball bearing between the hub and the axle of a ceiling fan and the bicycle.

Coal tar is a black thick liquid with an unpleasant smell. Products obtained from coal tar are used as starting material for manufacture of many dyes, drugs, explosives, perfumes, plastics, paints, photographic materials, roofing materials etc. Naphthalene balls used to repel moths and other insects are also obtained from coal tar.

The force responsible for changing the state of motion of ball is the force of friction. The ball will come to rest position. This force causes wear and tear of the objects in motion.

These days the head of the match sticks contains only antimony trisulphide and potassium chlorate. The rubbing surface has powdered glass and a little red phosphorus. When the match stick is struck against the rubbing surface i.e., some red phosphorus, this immediately reacts with potassium chlorate on the match stick head to produce enough heat to ignite antimony trisulphide and start combustion.

Types of combustion: It is of three types:
(i) Rapid combustion: When gases burn rapidly to produce heat and light, it is called rapid combustion.
(ii) Spontaneous combustion: When material suddenly bursts into flame, without the application of any apparent cause, it is called spontaneous combustion.
(iii) Explosion: When combustion takes place with sudden release of heat, sound, light and gas with a bang it is called explosion.

Pressure = \(\frac{Force}{Area}\)
For area, A = 8m²
\(p=\frac{200}{8}=25\) N/m² or 25 Pa

If despite favourable climatic conditions, farmer's crop failed to give good yield, the possibilities may be
(i) he did not use good quality and healthy seeds.
(ii) his field was not well irrigated.
(iii) manures/fertilisers were not timely and properly applied.
(iv) weeds were not removed.
(v) seeds were not sown at appropriate distance.
(vi) the soil was not ploughed and levelled properly.

Fertilisers are chemical substances that have a particular plant nutrient in concentrated form. They differ from manure on the basis of formation as these are produced in factories while manure can be prepared by farmer himself on the fields.

(i) The continuity of the forest is distributed animals get confined to smaller area. This leads to fragmentation of species and disturbance to the ecological balance. The noise of the vehicles will disrupt the silence of the forest, forcing the animals to move out into human habitations.
(ii) Forests are useful to mankind due to following reasons:
(a) Provide us fresh air and a wide variety of flora and fauna.
(b) Sources of various products such as paper, fibre, medicines etc.
(c)Keep the environment healthy and beautiful.
(iii) Amit has love for nature and environment. He is intelligent, calm and focussed.

When an animal is killed illegally, it is called poaching. It usually occurs when an animal possesses something that is considered valuable.
Effect of Poaching on environment : The whole ecosystem is affected due to harm caused on animal population. Everything from the animals to the plants and even the people in a specific place is negatively affected. We need various species of flora and fauna in our environmental ecosystem so that it is balanced and healthy. Our own survival depends on it.
Effect of Poaching on humans : Two serious problems are faced by humans, first is spread of food-borne illnesses e.g., Ebola and anthrax and second major affect is depletion of natural resources.

(a) She turned her car towards the ploughed field to protect herself from an accident.
(b) Since, the car moved from road to the ploughed field due to which the force of friction between the tyre and the ground surface increases suddenly. Because the large amount of irregularities reduces the movement of tyre. Thus, the car came to a rest.
(c) The values displayed by Shradha are intelligence and awareness.

(a) Sumit applied more pressure on his palm by baring the maximum load of his body on small  area of palm while Amit applied less pressure on his palm by baring the same load on larger area of palm.
(b) Amit have the presence of mind and he thought of an excellent idea about pressure on the body part.

Pouring water to extinguish the fire due to oil was not suitable action. It is because oil is lighter than water. So, water will settle down below the oil. In such condition, sand or soil should be used. They cut off the supply of air to the fire. Thus, fire can be controlled. But sand or soil will not be available at that place. So, Manu should have switched off the flame of the burner and put a lid on the frying pan. By doing this, the contact between fuel and oxygen is cut off and the flame will go off.

(a) A is petroleum and B is natural gas.
(b) A is thick liquid while B is gas.
(c) C is called fractional distillation
(d) D is kerosene.

(a) Paddy is cultivated in rainy season as it is a kharif crop.
(b) For sowing paddy, seeds are first grown in a nursery and later seedling are transplanted in the field. This allows us to select only healthy and better seedlings for cultivation.
(c) Measures taken to prevent spoilage or damage of harvested crops from insect attack are:
(i) Exposing them in sunlight for drying as freshly harvested crops have moisture.
(ii) Dried neem leaves are added to stored grains, so as to prevent damage from pests.
(iii) Specific chemical treatments are also available for preventing crops.