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22 September 2014

Wind Storm and Cyclone :Natural Phenomena: 7th class Hots Questions

Question: 1. Why are people advised not to stand near fast moving train?

Ans: When train moves with high speed it creates region of lower pressure . This low pressure  push man towards the train
Question: 2. Why are holes made in huge hoardings? Explain their usefulness.
Ans:  Holes are made in huge hoardings to reduce air pressure causing it to flutter or blown away.

Question: 3. in winter regions near, why does wind blow from land to sea?

Ans:. In winter the sea become warmer quickly than the land. So In winter monsoon blows from land to sea

Question: 4. Why are things colorful in appearance?

Ans: The colour of object is colour that is reflected. Thus different coulor makes things colourfull.

Question: 5. Fill the missing word in the blank spaces in the following statements:

(a)  Wind is moving air.

(b) Winds are generated due to uneven heating on the earth.

(c) Near the earth’s surface warm air rises up whereas cold air comes down.

(d) Air moves from a region of high pressure to a region of low pressure.

Question: 6. Suggest two methods to find out wind direction at a given place.

Answer:  Two methods to find out wind direction at a given place are:

a.  An instrument called anemometer can be used to find the direction and speed of the wind.

b.  Hold a strip of paper outside. The direction in which the paper is blowing is the direction of the flow of 
the wind.

Question: 7.  State two experiences that made you think that air exerts pressure.

Answer:  Two experiences that made us think that air exerts pressure are:

1.  Whiling cycling against the direction of the wind, it is difficult to ride. It shows that the air exerts pressure.

2.  While rowing a sailboat in the direction of the wind, it is always easier to row and while rowing a sailboat 
against the direction of the wind, it is very difficult to row. It also shows that the air exerts pressure.

Question: 8. You want to buy a house. Would you like to buy a house having windows but no ventilators? 
Explain your answer.

Answer:   No, I would not like to buy a house having windows but no ventilators. Warm air rises up and 
cool air comes downward. So, to make a stream of cool and fresh air to continuously flow to the house 
through the windows, there must be some ventilators in the upper part of the wall.

Question: 9.  Explain why holes are made in hanging banners and hoarders.

Answer:  Holes are made in hanging banners and hoarders to allow air to pass through them as a result of 
which there will be less pressure of air on the banners or hoarders. Unless it is done, these may be uprooted 
or distorted due to the pressure of the air.

Question:10  How will you help your neighbours in case cyclone approaches your village/town?

(a) I will help my neighbours in case cyclone approaches my village/town by the following ways.

(b) I will help my neighbours in shifting their household articles, domestic animals etc to a safe place.

(c) I will provide phone numbers of all emergency services like police, fie brigade and medical centers.

(d) I will give them safety advice like avoiding driving on roads through standing water, not touching wet 
switches etc.

Question: 11.What planning is required in advance to deal with the situation created by a cyclone?

Answer:  A good planning in advance will minimize the damages to be caused by a cyclone. Hence, the 
following planning is required.

(a)  The cyclone warning issued by the meteorological department through television, radio or news papers 
must not be ignored and followed carefully.

(b) The household articles, domestic animals, vehicle etc should be shifted to safe places.

(c) The telephone numbers of essential services like police, fie brigade and medical centers etc should be 
kept ready to meet the emergency    situation.

Question: 12. Which one of the following place is unlikely to be affected by a cyclone.

a) Chennai     2.  Mangaluru     iii) Amritsar                  d) Puri

Question: 13. Which of the statements given below is correct?

i) In winter the winds flow from the land to the ocean.

ii)In summer the winds flow from the land towards the ocean

iii) A cyclone is formed by a very high-pressure system with very high-speed winds revolving around it.

iv) The coastline of India is not vulnerable to cyclone

Question: 14.What is the Beaufort scale
The Beaufort scale is an empirical measure for the intensity of the weather based mainly on wind power
The scale was created by the British naval commander Sir Francis Beaufort around 1806

Question: 14.What is tornado?

Answer: A tornado is a violently rotating column of air that is in contact with both the surface of the earth

VII-Science- Winds, Storms and Cyclones CBSE Test Paper                     Download File
CBSE Class-7th Science Weather, Climate and Adaptations of Animal       Download File

13 August 2014

Physics numerical of chapter 10 gravitation class 9

Physics numerical of chapter 10 gravitation class 9- Part-01

1. The gravitational force between two objects is F. How will this force change when (i) distance between them is reduced to half (ii) the mass of each object is quadrupled?

2. A sphere of mass 40kg is attracted by a second sphere of mass 15kg when their centers are 20 cm apart, with a force of 0.1 milligram weight. Calculate the value of gravitational constant.

3. A body of mass 1 kg is placed at a distance of 2m from another body of mass 10kg. At what distance from the body of 1 kg, another body of mass 5 kg be placed so that the net force of gravitation acting on the body of mass 1 kg is zero?

4. A geostationary satellite is orbiting the earth at a height 5 R above the surface of earth, where R is the radius of earth. Find the time period of another satellite at a height of 2 R from the surface of earth.

5. The distance of planet Jupiter from the sun 5.2 times that of Earth. Find the period of revolution of Jupiter around sun.

6. If the distance of Earth from the Sun were half the present value, how many days will make one year?

7. Two satellites of a planet have periods 32 days and 256 days. If the radius of orbit of former is R, find the orbital radius of the latter.

8. The mass of Earth is 6 x 1024 kg and that of moon is 7.4 x 1022 kg. If the distance between the Earth and the Moon is 3.84 x 105 km, calculate the force exerted by Earth on the Moon. Given G = 6.7 x 10–11 Nm2/kg2.

9. If the distance between two masses is increased by a factor of 4, by what factor would the mass of one of them have to be altered to maintain the same gravitational force?

10. Two bodies A and B having masses 2kg and 4kg respectively are separated by 2m. Where should a body of mass 1kg be placed so that the gravitational force on this body due to bodies A and B is zero?

11. The mass of Sun is 2 x 1030 kg and mass of Earth is 6 x 1024 kg. If the distance between the centres of Sun and Earth is 1.5 x 108 km, calculate the force of gravitation between them.

12. Two electrons each of mass 9.1 x 10–31 kg are at a distance of  10A0. Calculate the gravitational force of attraction between them. Given 1A0 =10-10m

13. The gravitational force between force two objects is 100 N. How should the distance between these objects be changed so that force between them becomes 50 N?

14. Calculate the force of gravitation between two objects of masses 80kg and 1200 kg kept at a distance of 10 m from each other. Given G = 6.67 x 10–11 Nm2/kg2.

15. Calculate the force of attraction between the Earth and the Sun, given that the mass of Earth is 6 x 1024 kg and that of sun is 2 x 1030 kg. The average distance between the two is 1.5 x 1011m.

Physics numerical of chapter 10 gravitation class 9- Part-02

1. Calculate the force of gravity acting on your friend of mass 60kg. Given mass of earth = 6 x 1024 kg and radius of Earth = 6.4 x 106m.

2. Mass of an object is 10kg. What is its weight on Earth?

3. What is the mass of an object whose weight is 49N?

4. An object weighs 10N when measured on the surface of the earth. What would be its weight when measured on the surface of the Moon?

5. An object is thrown vertically upwards and rises to a height of 10m. Calculate (i) the velocity with which the object was thrown upwards and (ii) the time taken by the object to reach the highest point.

6. A force of 2 kg wt. acts on a body of mass 4.9kg. Calculate its acceleration.

7. A force of 20N acts upon a body weight is 9.8N. What is the mass of the body and how much is its acceleration?

8. A body has a weight of 10 kg on the surface of earth. What will be its mass and weight when taken to the centre  of earth?

9. How much would a 70 kg man weigh on moon? What will be his mass on earth and moon? Given g on moon = 1.7 m/s2.

10. The Earth’s gravitational force causes an acceleration of 5 m/s2 in a 1 kg mass somewhere in space. How much will the acceleration of a 3 kg mass be at the same place?

11. A particle is thrown up vertically with a velocity of 50m/s. What will be its velocity at the highest point of the journey? How high would the particle rise? What time would it take to reach the highest point? Take g = 10 m/s2.

12. If a planet existed whose mass was twice that of Earth and whose radius 3 times greater, how much will a 1kg mass weigh on the planet?

13. A boy on cliff 49m high drops a stone. One second later, he throws a second stone after the first. They both hit the ground at the same time. With what speed did he throw the second stone?

14. A stone drops from the edge of a roof. It passes a window 2m high in 0.1s. How far is the roof above the top of the window?

15. A stone is dropped from the edge of a roof. (a) How long does it take to fall 4.9m ?
(b) How fast does it move at the end of that fall? (c) How fast does it move at the end of 7.9m? (d) What is its acceleration after 1s and after 2s?

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29 July 2014

IX Bio. Why do we fall ill? NCERT solved questions

Q. What is an antibiotic? Give its one example 

Ans: Antibiotic is a chemical substance that kill bacteria, secreted by microorganismswhich can kill the pathogens Example – Penicillin 

Q. (i) Which disease is more harmful : Acute or Chronic disease ? Why? 
(ii) Why are we advised to take bland and nourishing food when we are sick? 

Ans: (i) Chronic disease 

Because chronic diseases have drastic long term effects on people’s health as compared to acute disease

(ii) (a) Such food does not contain oil or fat and spices so it is digested easily

(b) It provides sufficient energy for recovery after the disease

(c) It provides adequate amount of nutrients required for regeneration of cells and tissues.

Q. (i) How atmospheric inert nitrogen gas is converted into usable nitrogenous form for the various life forms? (ii) Draw a labelled diagram to show nitrogen cycle in nature
Ans: (i) (i) By the help of free living nitrogen fixing bacteria or nitrogen fixing bacteria found in roots of legumes.

(b) Physical process : During lighting, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen. These oxides dissolve in water to give nitric and nitrous acids and fall on land along with rain.

Q. (i) What are the consequences of Global warming (ii) Why is water essential to life?
Ans: (i) Rise in temperature (ii) Melting of glacier

(ii) (a) All life processes require water. (b) Water is needed for transportation of substances from one part of body to other in dissolved farm.

Q. Name the causal organism of AIDS. Why a person suffering from AIDS cannot fight even very minor infections ?
Ans: HIV (virus)

The virus goes to the immune system and damages its function. So the body can no longer fight off even minor infections.

Q. Write the symptoms when following organs are targeted by microbes. (a) Lungs (b) Liver (c) Brain.
Ans: Lungs – cough , breathlessness. Liver – Jaundice Brain – Headache, vomiting, fits

Q. What is immunization? List two diseases against which vaccines are available.
Ans: Immunization is the process in which a person's immune system is enhanced by giving inactive form of the disease causing agent ( immunogen). This agent develops the human immune system to fight against that agent and if attacked again by the same agent the immune systems give a more stronger response and eliminate the disease.

Two diseases for which vaccines are available are Polio and Diphtheria.

Q. Write the full form of AIDS. List four modes of transmission of virus of this disease.
Ans: Aquired Immuno Deficiency Syndrome

Modes of transmission of virus of this disease

a) Through sexual contact

b) Through blood trsnsfusion From mother to child

c) Through infected needled or syringes

Q. Health workers are exposed to more sick people than others in the community. Writeany four preventive measures they take to avoid sickness.
Ans: Preventive measures:

(i) Hand washing after any direct contact with patients

(ii) Wearing gloves while treating or examining the patient.

(iii) Proper disposal or sterilizing the instruments.

(iv) Immunisation.

Q. Same drug does not work against the microbes belonging to different groups. Why? State the mechanism of antibiotics in killing bacteria.
Ans: Every micro organism has its own biochemical cycle. So one type of antibiotic can stop or block biochemical cycle of one type of micro organism only but not all type of micro organisms. Antibiotic destroy the cell wall during the asexual reproduction cycle hence the bacteria can be easily killed.

Q. “Water is essential for living organisms”. State two reasons to justify this statement.
Ans: Water is needed by organisms to maintain their body temperature. Water is needed by organisms to perform many biochemical reactions.

Q. List the names of three diseases caused by virus stating their mode of communication in each case.
Ans: (1) Influenza (2) Hepatitis (3) AIDS

Mode of communication

(1) Blood transfusion (2) Unprotected sexual contact (3) Use of contaminated needles syringes etc. (4) From mother ‘to foetus thmyh’ placenta

Q. List four preventive measures against communicable diseases.
Ans: 1. Health education 2. Isolation 3. Proper sanitation 4. Sterilization of articles used by patients 5. Vaccination 6. Provision of safe water supply

Q. A person has lost his power to fight infections. Name the disease the person is suffering from. State the pathogen and modes of transmission of this disease.
Ans: Suffering from AIDS Name of pathogen is a virus known as HIV. Mode of transmission of HIV is :

1. Intimate sextual contact

2. Blood transfusions

3. Contaminated needles, syringes or razors (Any 2 points)

Check it out

Class IX Biology Chapter - Why do we fall ill?   NCERT Solutions
CCE Test Paper Biology     Chapter:  Why do we fall ill?   Solved Questions
NCERT Solved Board Questions 9th Science: Ch-13.  Why do we fall ill?
Class IX  Biology Ch-13.Why do we fall ill-Chapter Notes