Exercises: Wind & Storm | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests PDF Download

Objective Type Questions 

Monsoon
Monsoon winds are seasonal winds that bring heavy rainfall to a particular region. These winds occur due to the differential heating of the land and sea.

Q.2. When air expands, its particles move________(closer/farther away). 

Farther away
When air expands, the distance between its particles increases. This happens because the pressure exerted by the air decreases, causing the particles to move away from each other.

Q. 3. A/An_______(wind vane/anemometer) can be used to measure wind speed. 

Anemometer

An anemometer is a device used to measure the speed and direction of wind. It consists of a set of cups that rotate with the wind, and the speed of rotation is proportional to the wind speed.

Q.4. High waves that form when a cyclonic storm moves towards land is called a _______(storm surge/water spout). 

Storm surge
A storm surge is a rise in sea level that occurs when a cyclonic storm moves towards land. The high winds and low atmospheric pressure associated with the storm cause the sea level to rise, resulting in high waves and flooding.

Q.5. You will not be able to outrun a___________ (tornado/breeze) in a car. 

Tornado
Tornadoes are extremely powerful and destructive storms that can move at speeds of up to 70 miles per hour. It is not safe to try to outrun a tornado in a car, as the storm can change direction quickly and cause significant damage. It is best to seek shelter in a sturdy building or underground.

B. Choose the correct option.

Very Short Answer Type Questions. 

Wind

Q.2. A scale used to represent the category of a cyclone__________

Cyclone

Q.3. Name for cyclone in East Asia __________

Typhoon

Q.4. When the eye of storm hits land __________

Landfall

Q.5. Tornadoes formed over sea __________

Waterspouts

Short Answer Type Questions 

The heating of the Earth is uneven because the Sun's rays fall directly on the equator and are spread over a larger area near the poles. This leads to temperature differences and results in the formation of winds and weather patterns.

Q.2. Why do rain-bearing winds from over the ocean blow towards the land in summer?

During summer, the land becomes hotter than the sea. This causes the air above the land to rise and cooler air from the sea moves in to replace it. This movement of air from the sea towards the land is called sea breeze and it brings rain-bearing winds with it.

Q.3. Why does warm air rise? 

Warm air rises because it is less dense than cold air. As air gets heated, its molecules move faster and take up more space. This makes the warm air less dense and lighter, causing it to rise above the denser, cooler air.

Q.4. Explain why roofs can be blown off during a storm. 

Roofs can be blown off during a storm because of the strong winds. These winds can create a difference in air pressure on both sides of the roof. The higher pressure on the outside of the roof pushes against it while the lower pressure on the inside creates a vacuum, lifting the roof off.

Q.5. Why does a wind vane point towards the direction of the wind? 

A wind vane points towards the direction of the wind because of the shape of its arrowhead. The arrowhead is designed to be heavier on one side and lighter on the other, with the heavier side facing away from the wind. This causes the vane to rotate until it points in the direction from where the wind is blowing.

Q.6. On what factors does atmospheric pressure depend upon? 

Atmospheric pressure depends on factors such as temperature, humidity, and altitude. As temperature increases, air molecules move faster, creating a higher pressure. Humidity affects pressure by changing the density of air. Altitude also affects pressure as air pressure decreases with increasing altitude due to the decreasing weight of the atmosphere above.

Long Answer Type Questions 

A wind is set up in the atmosphere due to differences in air pressure caused by uneven heating of the Earth's surface. The Sun's rays fall directly on the equator, making it warmer than the poles. As warm air rises from the equator, cooler air from the poles moves in to replace it, creating a movement of air known as wind. This process is known as convection. The rotation of the Earth also influences the direction of winds, causing them to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. These movements of air are responsible for weather patterns and play an important role in regulating the Earth's climate.

Q.2. Describe a simple experiment to show that air in the atmosphere exerts pressure.

To show that air in the atmosphere exerts pressure, you can conduct a simple experiment using a plastic bottle, a balloon, and a straw. First, inflate the balloon and attach it to the end of the straw. Then insert the straw into the bottle and seal the opening with a rubber stopper. Next, squeeze the sides of the bottle to reduce its volume. As you do this, you will notice the balloon getting larger. This happens because the air inside the bottle is being compressed, causing its pressure to increase. The higher pressure of air inside the bottle then pushes the balloon out of the straw, demonstrating that air exerts pressure.

Q.3. You are given a fully blown balloon, a tub of hot water, and a tub of ice-cold water.  Using these items, explain how you would show that air expands on heating and contracts when it cools down.

To demonstrate that air expands on heating and contracts when it cools down, you can use the following steps. First, place the fully blown balloon in the tub of hot water. As the air inside the balloon heats up, it will expand and cause the balloon to inflate further. Next, remove the balloon from the hot water and place it in the tub of ice-cold water. As the air inside the balloon cools down, it will contract, causing the balloon to deflate. This experiment shows that air expands on heating and contracts when it cools down.

Q.4. Draw a diagram and explain briefly how a cup anemometer works.

A cup anemometer is an instrument used to measure wind speed. It consists of a central axis with three or four cups attached to the ends of horizontal arms. The cups are shaped like small cups or buckets, with the open ends facing the direction of the wind. When the wind blows, the cups rotate around the axis, with the speed of rotation being proportional to the wind speed. A mechanism inside the anemometer is used to count the number of rotations and convert it into a measurement of wind speed. The cup anemometer is widely used in weather stations and can be used to measure both low and high wind speeds.