Question

Car tyres are made of rubber and not of iron because
1) Rubber is cheaper than iron
2) iron tyres produce noise
3) Rubber can giver circular shape easily than iron
4) Friction between rubber & concrete is less than that between iron & concrete

Answer 1

Hint: Iron is much harder than rubber. For making tyres, we require a material which can be made into desired shape and can be inflated and deflated. Iron is much more elastic than the rubber due to which it does not show these desired properties to make tyres.

Complete answer:
For making tyres for vehicles, we require a type of material which can be made into tyre shape easily. Iron is a lot harder than the rubber and requires more force and effort. Since rubber can be given a circular shape much more easily than iron, the car tyres are made of rubber and not of iron.

So, the correct answer is “Option C”.

Additional Information:
Elasticity of a material can be defined as the ability of a material to regain its original shape after an external force is applied on it. The ratio of stress applied on a body to the strain produced in it is defined as the Young’s modulus of that material.
Now, when we apply equal amounts of stress on steel and rubber having the same cross-sectional area, we notice that compared to steel, rubber gets stretched. The strain produced in rubber is much larger compared to that in steel. This means that steel has a larger value of Young’s modulus of elasticity and hence, steel has more elasticity than rubber.
Greater the resistance to change, greater is the elasticity of that material. Rubber gets stretched because there is strain produced in it when stress is applied. The larger strain means the material is less elastic.

Note:
The other options given to us are also correct in themselves but the first thing that needs to be taken into consideration is the property of material, if it can be made into a wheel easily or not. Things like price and friction are considered later.