Active Science Solutions for Class 7 Science Chapter 8 The Weather, Climates And Storms are provided here with simple step-by-step explanations. These solutions for The Weather, Climates And Storms are extremely popular among class 7 students for Science The Weather, Climates And Storms Solutions come handy for quickly completing your homework and preparing for exams. All questions and answers from the Active Science Book of class 7 Science Chapter 8 are provided here for you for free. You will also love the ad-free experience on Meritnation’s Active Science Solutions. All Active Science Solutions for class 7 Science are prepared by experts and are 100% accurate.

Page No 111:

Question 1:

Wind currents are caused due to
(a) convection currents across land and sea.
(b) a combination of convection currents and rotation of the earth.
(c) the earth's rotation.
(d) convection currents only.

Answer:

(a) convection currents across land and sea
The convection currents due to warm and cold air across the land and sea cause winds.

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Question 2:

Which of the following should not be done in a cyclone-hit area?
(a) Do not touch power lines that have been brought down.
(b) Do not touch wet switches.
(c) Do not store drinking water for emergencies.
(d) Do not ignore warnings issued by the meteorological department.

Answer:

(c) Do not store drinking water for emergencies.
Drinking water should be stored during cyclone for emergencies.

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Question 3:

The factors that contribute to the formation of cyclones are __________________.
(a) wind speed
(b) temperature
(c) humidity
(d) all the above

Answer:

(d) all of the above
Formation of cyclone requires high temperature and humidity along with high-speed wind currents.

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Question 4:

Which one of the following explains why wind flows near the equator?
(a) The equator gets more heat energy from the sun causing the regions around it to be warmer.
(b) Warm air rises and the cooler air from 30 degrees latitude belt on either side of the equator moves in.
(c) These winds blow from the north and the south towards the equator.
(d) all the above.

Answer:

(d) all of the above
The light from the sun is at its maximum at the equator than at the poles. Thus, equator receives maximum heat and air around it is warmer. The warm air is lighter, so it rises up and is replaced by the cooler air from 30 degrees latitude belt on either side of the equator. These winds blow from the north and the south towards the equator.

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Question 5:

Which of the following is a characteristic of the region surrounding the eye of a cyclone?
(a) high speed winds
(b) low speed winds
(c) high speed rotating winds.
(d) low speed rotating winds.

Answer:

(b) low speed winds
In the eye of a cyclone, the winds are like light breeze.

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Question 6:

Increase in wind speed is accompanied by
(a) increase in pressure
(b) increase in humidity
(c) decrease in pressure
(d) decrease in humidity

Answer:

(c) decrease in pressure
Fast-moving winds exert less pressure compared to slow-moving winds.

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Question 7:

A typhoon is also known as a _____________________.
(a) cyclone
(b) tornado
(c) volcano
(d) earthquake

Answer:

(a) cyclone
A typhoon is also known as a cyclone.

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Question 8:

Which of the following should people avoid in case of a cyclone?
A. ignoring warnings.
B. keeping essential commodities handy
C. walking on flooded roads.
D. contact with broken power lines
E. cooperating with friends and neighbours
F. loose and hanging objects
G. leaving the electrical appliances at home plugged in

(a) A, C, D, G
(b) A, C, D, F, G
(c) B, E, F
(d) B, E, F, G

Answer:

(b) A, C, D, F, G
In case of cyclones, a special attention should be given to warnings and essential commodities should be kept handy. Walking on flood and contact with broken power lines should be avoided as it can be dangerous.

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Question 9:

When we look out the classroom window, are we observing climate or weather?

Answer:

When we look out of the classroom window, we observe weather. Weather is the local state of environment of a given area, whereas climate is the atmospheric condition of a wide area over a long period of time.

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Question 10:

What is the difference between weather and climate? Give reasons for your answer.

Answer:

Weather Climate
It is the  atmospheric condition at the specific place at specific time. It is the average of the weather conditions of a place over a large time span like 20–25 years.

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Question 11:

Describe the two situations that result in the formation of wind currents.

Answer:

The equator receives more heat than polar regions. Thus, the air around equator absorbs more heat and is warm. The warm air rises up and the cooler air from the poles rushes there. Thus, by convection, the wind currents are formed.
The other situation that results in the formation of wind currents is that land absorbs more heat as compared to sea during daytime. During the daytime the air above the land gets warm and rises up and the cooler air from sea moves towards the land. During night, the land loses heat faster as compared to sea. Thus, in night, the air above sea is hotter and cool air from land rushes towards it. This leads to the formation of wind currents.



Page No 112:

Question 12:

Raghav placed a small coin on a table about 1cm from the edge. He then bent down so that his mouth was level with the tabletop, and blew hard across the top of the coin. He found the coin jumping. Why do you think this happened? (Try it yourself.)

Answer:

When Raghav blew hard across the top of the coin, he found the coin jumping because the air blown out has high speed and thus low pressure; so, air on the surface of the coin has high pressure. Also, air moves from area of high pressure to low pressure. This air movement caused the coin to jump.

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Question 13:

(a) Fill in the blanks with appropriate words.
When air _______________(heats/cools), the air molecules _____________(spread out/come closer) so that there are fewer air molecules in the same space. _______________(Warm/Cool) air weighs less than _______________ (Warm/Cool) air, which means that warm air presses down on the earth less than cool air. Less pressing means _____________ (less/more) pressure. Thus, a mass of warm air creates an area of low pressure. Warm air rises and produces clouds. So, _______________ (low/high)pressure areas usually bring rain or storms.
(b) Now, explain how high pressure areas are associated with clear skies.

Answer:

(a) When air heats, the air molecules spread out so that there are fewer air molecules in the same space. Warm air weighs less than cool air, which means that warm air presses down on the earth less than cool air. Less pressing means less pressure. Thus, a mass of warm air creates an area of low pressure. Warm air rises and produces clouds. So, low pressure areas usually bring rain or storms.

(b) The high pressure areas have slow-moving air and thus, clouds cannot be formed; therefore, such areas are associated with clear skies.

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Question 14:

How are winds formed?

Answer:

The winds are formed because of the movement of air that carries warm air away from the tropics and cool air away from the poles. Equator receives more heat from sun; hence, the air around it gets warm. Warm air being light rises up and the cooler dense air from poles moves towards this space causing the wind currents.

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Question 15:

What precautions should you take if you are living in a cyclone-prone area?

Answer:

Following precautions should be taken if you are living in a cyclone-prone area:

  • Store drinking water for each family member in airtight container.
  • Keep first-aid box with you.
  • Keep good quality torch, spare batteries and radio handy.
  • Keep essential commodities like food items in case of emergency.
  • Do not touch power lines and keep away from the loose hanging objects.

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Question 16:

Explain the formation of a cyclone.

Answer:


Water on the surface of the Earth absorbs heat and changes to vapour. As water vapour moves up higher in the atmosphere, it carries this heat along with it. The higher regions of the atmosphere are cooler. This condenses the water vapour into water drops.
When vapour cools down, it releases the absorbed heat into the atmosphere. The heat thus released warms up the air and causes it to rise up once again. A low pressure area is thus formed and the air from the surrounding areas rushes in. This sequence of events is repeated continuously.
Thus, this cycle is the result of the formation of a very low pressure system with high wind speeds revolving around it. This weather phenomenon is known as a cyclone.

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Question 17:

What happens to the pressure of wind if its speed increases? Describe an experiment to prove it.

Answer:

The pressure of wind decreases when its speed increases.

Experiment:
Take two paper strips of 20 cm × 3 cm in each hand, facing each other in front of your mouth around 12 cm apart. Blow air between the strips. This will drop the air pressure between them as compared to stationary air around them, and they will separate. The greater pressure of surrounding air pushes the strips together. This shows that high speed wind has low pressure.

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Question 18:

Give reasons for the following:
(a) A hot can gets distorted when water is poured over it.
(b) A paper kept at the mouth of a bottle does not go inside if we blow air on the mouth of the bottle.

figure

(c) Cyclones are destructive.
(d) A student did an experiment as shown here. When she blew through the horizontal straw, a spray of water flowed out from the vertical straw.

figure

Answer:

(a) A hot can is filled with air. When water is poured over it, the air in the can is displaced and the can gets distorted.

(b) When we blow air at the mouth of the bottle, the air pressure decreases in the neck of the bottle because moving air exerts less pressure. Therefore, a paper kept at the mouth of a bottle does not go inside.

(c) Cyclone is a large mass of air rotating violently. The air rotates faster and can break houses and carry away the nearby things. Hence, cyclones are destructive.

(d) When a student blew through the horizontal pipe, the air pressure was decreased over the vertical straw, creating a little vacuum like space. This made a spray of water to flow out of it to fill that space.

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Question 19:

List some safety measures that people should take during a cyclone.

Answer:

The safety measures that people should take during a cyclone are as follows:

  • Keep radio and television on to hear emergency broadcast.
  • Leave homes in case of flood warnings. Turn off electricity, gas and water supply before you leave.
  • All electrical appliances should be unplugged.
  • Stay indoors until and unless it is announced that going outside is safe.
  • When outdoors, do not touch any power lines and stay away from loose hanging objects.



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