Q.6 (a) Define a cell. Who discovered the cell?
(b) Why is nucleus considered the brain of the cell?
Q.7 (a) Voice of women is usually shriller as compared to men. Why?
(b) What do you understand by reverberation?
Q.8 (a) Define pressure. What is the SI unit of Pressure?
(b) It is difficult to cut a small piece of eraser using blunt side of a knife. Why?
Q.9 (a) Mention 2 characteristics that make the earth an ideal place to support life.
(b) What are meteorites?
Q.10 (a) What do you understand by treading of tyres?
(b) How does friction help in walking?
Q.11 (a) The destruction of an animal’s habitat affects not only that species, but other animals & humans
as well. Explain this statement.
(b) What is the difference between extinct & endangered species?
Q.12 (a) What is comet? What is the time period of Halley’s comet?
(b) The distance of the celestial bodies is measured in the light years. Why?
Q.13 (a) Expand the following
(1)CNG
(2) LPG
(3) SPM
(4) CFC
(b) What is greenhouse effect?
Q.14 (a) Define reflection. State the laws of reflection.
(b) What kind of reflection occurs when reading a newspaper?
Q.15 Explain any 3 applications of pressure.
OR
Explain any 3 effects of force with example.
Q.16 What is acid rain? Discuss the ill-effects of acid rain.
OR
How can frictional force be minimised? Explain.
Q.17 Write the characteristics of the images formed by a plane mirror.
Q.18 With the help of an experiment prove that sound needs a medium to travel.
(Draw neat, labelled diagram).
Answers
Answer:
a)Cells are the fundamental structural units of living organisms and the basic units of life. ... Robert Hooke discovered the cell in the year 1665 as a thin section of cork under the self made microscope.
c) The nucleus is called the "brain" of the cell because it holds the information needed to conduct most of the cell's functions. Other molecules make proteins from that information on a regular basis - each moment of our lives
c)i) Women have shorter vocal cords which vibrate more quickly and produce a higher pitch, while in men the longer vocal cords vibrate with low frequencies giving them deeper voice. Thus, women have high-pitched or shriller voice as compared to men.
ii) A reverberation, or reverb, is created when a sound or signal is reflected causing numerous reflections to build up and then decay as the sound is absorbed by the surfaces of objects in the space – which could include furniture, people, and air.
d) Pressure is the amount of force applied perpendicular to the surface of an object per unit area and the for it is p (or P). The SI unit for pressure is the pascal (Pa), equal to one newton per square metre (N/m2, or kg·m−1·s−2)
Why does the sharper side of a knife cuts more easily than the blunt side of it? A sharp side of knife has a smaller contact area. Therefore, for the same amount of force applied on it, the sharp side of knife exerts more pressure than the blunt side and hence cuts more easily.
Importance of Earth's Atmosphere.
Importance of Ozone Layer.
Favourable Climatic Condition.
Water.
Force of attraction (Earth's gravitational pull)
A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the atmosphere to reach the surface of a planet or moon
The treading of a tire or track refers to the rubber on its circumference that makes contact with the road or the ground. As tires are used, the tread is worn off, limiting its effectiveness in providing traction. A worn tire can often be retreaded.
So, a normal reaction by the foot on to the ground gives rise to frictional force, which pushes us forward. Complete step by step solution: ... The horizontal frictional force acting towards the right, which acts opposite to the effective horizontal force applied by our foot prevents us from slipping while walking
if we destroy the animal habitat then we not only affect that animal but we affect the whole food web. ... when there would be no animals it would affect humans in indirect way as they won't get the fossil fuels which are very important at this time
Extinct species are the organisms that have become extinct either in the wild or completely. An endangered species is a species of organisms facing a very high risk of extinction.
75 years
Halley's Comet is arguably the most famous comet. It is a "periodic" comet and returns to Earth's vicinity about every 75 years, making it possible for a human to see it twice in his or her lifetime. The last time it was here was in 1986, and it is projected to return in 2061.
The light year is used to measure distances in space because the distances are so big that a large unit of distance is required.
CNG- compressed natural gas
LPG-liquified petroleum gas
SPM-social performance management
Cfc- Chlorofluorocarbon
Answer:
same answer he say it is right