NCERT Class VII: Science-Exercise Solutions

NCERT Book Exercise Page Number-92
Q.1. Fill the missing word in the blank spaces in the following statements:
(a) Wind is________ air.
(b) Winds are generated due to_______ heating on the earth.
(c) Near the earth’s surface __________air rises up whereas ___________ air comes down.
(d) Air moves from a region of _______ pressure to a region of_____ pressure.
Answer:
(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 cooler air comes down.
(d) Air moves from a region of high pressure to a region of low pressure.
Q.2. Suggest two methods to find out wind direction at a given place.
Answer:
The two methods to find out in which direction wind is blowing are as follows:-

i. If we fly a kite, the direction in which kite flies tells about the direction of the wind.

ii. When we put our clothes to dry, the direction in which clothes will be carried away tells about the direction of the wind.

Q.3. State two experiences that made you think that air exerts pressure
(Other than those given in the text).
Answer: Two experiences which make us think that air exerts pressure are as follows:-
(i) When we inflate a balloon, after sometime even if we blow air the balloon won’t inflate any more. It might burst but will not inflate because air exerts pressure.
(ii) When we open the window panes the curtains tend to move, this movement is due to the pressure exerted by the wind.

Q.4. 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 which has windows but no ventilators because windows are located at the lower height but the ventilators are at the higher height. Ventilators help the room to be cool because warm air will start rising and as ventilators are present so the warm air will come out through the ventilators.