8 What does PCRA stand for?
9 What is atmospheric pressure?
SECTION-D
IV] LONG ANSWER TYPE QS.
10 Explain an actvity to show that liquid pressure depends on the length of the column of liquid.
11 What are signifcance of ploughing a feld?
SECTION-E
V] THINK AND ANSWER:-
12 Why is it difcult to cut with a blunt knife?
13 What will happen if wheat is planted as kharif crop?
14 Can you think of any substtute of fossil fuels?
15 Why are oil wells found in water bodies?
Answers
Answer:
pcra stands for petroleum conservation reserch association
Answer:
8 petroleum conservation research association
9 Atmospheric pressure, also known as barometric pressure, is the pressure within the atmosphere of Earth. The standard atmosphere is a unit of pressure defined as 101,325 Pa, which is equivalent to 760 mm Hg, 29.9212 inches Hg, or 14.696 psi.
10
◆Take a plastic bottle or a beaker which has tube like structure.
◆Fill the container full with water.
◆Now with any sharp object make holes to the container one by one from top to bottom.
◆You can observe that water flowing out from top holes are coming with less force and falling just infront of the beaker.But the water flowing out from bottom holes are coming with higher force and falling far from container.
◆Repeat the same experiment with half filled container . you will notice change in flow of water outside.
11 The prime purpose of ploughing is to turn over the uppermost soil, so bringing fresh nutrients to the surface, while burying weeds and crop remains to decay. Trenches cut by the plough are called furrows. In modern use, a ploughed field is normally left to dry and then harrowed before planting
12 Hence, when we use a blunt knife, as force is applied on more area, pressure is less and it is difficult to cut vegetables. As in the property the pressure and area is inversely proportionate that means if the area is more pressure exerted will be less as the pressure will be distributed in the area
13 If wheat is sown in the kharif season (from June to October), then the whole crop might get destroyed because of many factors such as lack of optimum temperature, adaptability, availability of pests, etc. Kharif season includes the rainy season, which is not favourable for the growth of wheat crop.
14 Some well-known alternative fuels include bio-diesel, bio-alcohol (methanol, ethanol, butane), refuse-derived fuel, chemically stored electricity (batteries and fuel cells), hydrogen, non-fossil methane, non-fossil natural gas, vegetable oil, propane and other biomass sources.
15 An oil well is a boring in the Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may be termed a gas well.
Explanation:
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