The correct option is (c) 1 and 3 only.
Explanation
Air is a mixture of gases that surrounds the Earth. When air is in motion, it is called wind. Moving air possesses kinetic energy and exerts pressure, which can apply force to objects, facilitating movement or generating lift.
Statement-wise Analysis:
- Statement 1 is Correct: A "firki" (pinwheel) operates on the principle of converting the kinetic energy of moving air into rotational mechanical energy. When wind strikes the blades of the firki, it creates a force that causes the blades to spin around a central axis.
- Statement 2 is Incorrect: Moving air is essential for the flying of kites. The movement of air across the surface of the kite creates a pressure difference (aerodynamic lift) that allows the kite to rise and stay aloft. Therefore, moving air facilitates, rather than hinders, the flying of kites.
- Statement 3 is Correct: The fluttering of pages in a book is caused by the force exerted by moving air. As air flows over or between the pages, it creates pressure variations and direct physical force, causing the lightweight paper to move or flutter.
Key Takeaway:
Wind (moving air) exerts force and pressure, which is the fundamental mechanism behind the movement of objects like pinwheels, the lift required for kites, and the displacement of light objects like paper.