Science, unit 9, unit 10

Lesson - 9

Uses of Wind and Water

Main Points to Remember

👉 The slow moving air is called as breeze and the fast moving air is called as storm.

👉 The moving air is useful to us in many ways.

👉 Moving air is useful to dry the clothes and sweat, to fly kites, to separate husk from grains and in hot air balloon.

👉 Fast moving air is used to run the windmill and to generate electricity.

👉 Nepal is very rich in fast moving water as it has many rivers flowing down.

👉 Moving water is very useful to us. It is used for irrigation and rafting.

👉 Moving water is used for running ‘Panighatta’ and to generate hydro electricity

Exercise

1. Fill in the blanks with suitable words

Answer 👉 

a. The slow moving air is called breeze.

b. Wind is needed for hot air ballooning.

c. Running water is needed to run panighatta.

d. In Nepal, there are many fast running rivers.

e. Grains are grinded in wind mill.

2. Write ‘True’ for the correct sentences and ‘False’ for the wrong ones.

a. The storm can cause many damages.

b. Fast moving air can be used to generate electricity.

c. Only sunlight is required for drying clothes.

d. Water falls from a certain height in a hydroelectricity project to rotate the turbine.

e. Rafting is done in lakes

Answer 👉 

a. True

b. True

c. False (Sunlight is not the only requirement for drying clothes. Wind also plays a significant role in drying clothes quickly.)

d. True

e. False (Rafting is typically done in rivers or whitewater rapids, not in lakes.)

a. Write down any four uses of moving air

Four uses of moving air are:

• Generating electricity through wind turbines.
• Aiding in flight for birds, insects, and other flying creatures.
• Facilitating ventilation and cooling in buildings.
• Supporting wind-based recreational activities like sailing and kite flying.

b. Write down any four uses of moving water.

Four uses of moving water are:

• Generating electricity through hydroelectric power plants.
• Facilitating transportation through rivers and canals.
• Supporting aquatic life and ecosystems.
• Providing water supply for agriculture, drinking, and other purposes.

c. How is electricity generated in hydro power station? Explain briefly.

Electricity is generated in a hydro power station by utilizing the force of falling water to rotate a turbine. Water from a certain height, such as a dam or waterfall, is directed towards the turbine. The force of the water causes the turbine to spin, which in turn rotates the generator. The generator converts the mechanical energy from the turbine into electrical energy, which is then transmitted for use.

d. Nepal has maximum capacity to produce electricity. Why?

Nepal has a significant capacity to produce electricity due to its abundant water resources, including numerous fast-flowing rivers and high mountain ranges. The country's topography provides ideal conditions for the development of hydroelectric power projects. Nepal's hilly and mountainous terrain allows for the construction of large dams and reservoirs, creating ample opportunities for harnessing the potential energy of moving water to generate electricity.

4. Draw the diagram of a pinwheel (paper fir fire) and colour it.

Answer 👉 Do yourself

Lesson - 10

The Weather

Main Points to Remember

👉 Weather is the condition of a day. It is affected by the clouds, sunshine, rain and wind.

👉 There are different types of weather like sunny, cloudy, rainy and cold.

👉 Water vapour at cold place forms cloud and cloud carries the rain.

👉 The slow moving wind is a breeze and fast moving wind is a storm.

👉 The moving wind is destructive which may destruct the natural and manmade things.

👉 Winter days are colder. In winters days we feel cold due to snow fall, fog, mist and frost.

👉 The extreme cold is difficult to survive. We must be protective in cold winter season.

Exercise

1. Fill in the blanks with suitable words.

Answer 👉 

a. Sunshine is the main factor that changes the weather.

b. The water vapor is lighter than cold air.

c. Storm causes destruction.

d. Snowfall occurs in Himalayan region.

e. Fog is a thick cloud close to the ground.

f. We feel cold when sunshine is blocked by cloud or fog.

2. Write ‘True’ for the correct sentences and ‘False’ for the wrong ones.

a. When air blows, clothes dry faster.

b. We feel cold during winter season..

c. A cloudy day is warmer than a clear day.

d. Fog decreases the visibility and may cause road accidents.

e. In winter, the sun lies far from the earth.

f. All the trees remain green in winter season.

Answer 👉 

a. True

b. True

c. False (A cloudy day is generally cooler than a clear day because clouds block sunlight and prevent it from warming the Earth's surface.)

d. True

e. True

f. False (Not all trees remain green in the winter season. Some trees shed their leaves and appear bare during winter, while evergreen trees retain their green foliage.)

3. Answer the following questions.

a. What is the weather? What are the factors affecting the weather?

Answer 👉 Weather refers to the atmospheric conditions at a specific place and time. The factors affecting weather include temperature, humidity, air pressure, wind speed and direction, and the presence of clouds and precipitation.

b. How does cloud form? Why is cloudy day colder?

Answer 👉 Clouds form when warm air rises and cools, causing the water vapor in the air to condense into tiny droplets or ice crystals. A cloudy day can be colder because the clouds block the sunlight, reducing the amount of solar radiation reaching the Earth's surface and thus decreasing the temperature.

c. Is it safe to walk out when there is storm outside? Why?

Answer 👉 It is not safe to walk out when there is a storm outside. Storms can be accompanied by strong winds, heavy rain or snow, and lightning, which pose various risks to personal safety. Strong winds can cause objects to be blown around, heavy rain can lead to flooding, and lightning can cause electric shocks and fires.

d. How does snowfall occur?

Answer 👉 Snowfall occurs when the temperature in the atmosphere is below freezing (0 degrees Celsius or 32 degrees Fahrenheit) and there is moisture present in the form of water vapor. The moisture condenses into ice crystals or snowflakes and falls to the ground.

e. Write any two ways that we can do to prevent from extreme cold.

Answer 👉 

Two ways to prevent from extreme cold are:

• Dressing warmly: Wearing multiple layers of clothing, including a hat, gloves, and a thick coat, can help insulate the body and retain heat.
• Stay indoors: Limiting exposure to extreme cold by staying indoors in heated spaces can help protect against the adverse effects of cold temperatures, such as frostbite and hypothermia.