Explain why:
(a)air is used to make inflate tyres.
(b)steel is used to make railway lines.
(a) Air is easily available and compressible.Therefore, it is used to inflate tyres.Other gases can also be used but their storage and use will be costly in comparison to air.So, air has a benefit of being cheap.
(b) Steel is a versatile material. If right composition and heat treatment method is used, it can be used to make many stucrures.Steel used for railway lines has a high tensile strength and appropriate hardness.It has resistance to internal and surface cracks.