Question

Which of the following is not a smooth surface:
A. Surface of wet soap
B. Surface of tyres
C. Glazed tiles
D. Surface of mirror

Answer 1

Hint: A smooth surface has no roughness, lumps, or holes. And if a surface is rough, it is uneven and not smooth.

Complete answer:
As we know that the surface of tyres is rough and uneven so we can say that the surface of a tyre is not a smooth surface.
Here, a smooth surface is a surface in which there are no holes or lumps. If we walk on a smooth surface there would be no heat generated due to the walking nor the sole of our shoes will be worn off. Also, if a surface does not have singular points on it, it is said to be a smooth surface. Smoothness of surface has a given condition: If the surface is parameterized in two variables u and v then it can be considered smooth if the tangential vectors in the directions of u and v satisfy:
${T_u} \times {T_v} \ne 0$
Surface with a minimum amount of friction or no friction is said to be a smooth surface. As we know that the friction is the force which is opposing in nature, so in a smooth surface there would be no opposing or frictional resistance so, the object can move without any trouble (smoothly) whereas a rough surface is a surface in which there would be a major amount of frictional force present, also it has many singular points, ridges, lump, etc which cause a restrain on the motion of the object on which it is moving.
Hence the correct option is (B).

Note:
When the object will move on a rough surface then it will be difficult for the object to move on that surface, which means that the friction will be high. Also, when the object will move on a smooth surface then it will be easy for the object to move on that surface, which means that the friction will be low.