The comparative form of smooth is smoother, not more smooth.
smoothestThe superlative of 'smooth' is ' smoothest'.
smoother
smoother,smoothest.
smoother
Both are correct grammatically in English. It is because smooth, smoother and smoothest are the three forms.
smoother is comparative of word smooth.
smoother
smoother, smoothest
by cleaning the surface
Because friction is less on smooth surfaces. Smoother the surfaces, lesser the friction.
Silk is smoother than wool.