Question

.Explain how the force of friction varies with nature of surfaces in contact and area of contact? Does force of friction also varies with the weight of the block?

Answer 1

The more the area of contact, the more the friction as there are tiny hills and valleys on the surfaces which get entangled.
The more the area of contact, the more the friction as on large surface, the hills and valleys will entangle in large number so more friction would be there.
Yes, the friction increases with an increase in the weight of the block!