gokulavarshini
Soft materials will deform when under pressure. This also increased the resistance to motion. For example, when you stand on a rug, you sink in slightly, which causes resistance when you try to drag your feet along the rug's surface. Another example is how rubber tires flatten out at the area on contact with the road. When materials deform, you must "plow" through to move, thus creating a resistive force.
Pushing object on soft surface When the deformation becomes large, such that one object sinks into the other, streamlining can affect the friction, similar to what happens in fluid friction.
Summary
The causes of the resistive force of friction are molecular adhesion, surface roughness, and the plowing effect. Adhesion is the molecular force resulting when two materials are brought into close contact with each other. Surface roughness is a factor in friction when the materials are rough enough to cause serious abrasion. When one or more of the materials is relatively soft, much of the resistance to movement is caused by deformations or a plowing effect
Answers & Comments
When materials deform, you must "plow" through to move, thus creating a resistive force.
Pushing object on soft surface
When the deformation becomes large, such that one object sinks into the other, streamlining can affect the friction, similar to what happens in fluid friction.
Summary
The causes of the resistive force of friction are molecular adhesion, surface roughness, and the plowing effect.
Adhesion is the molecular force resulting when two materials are brought into close contact with each other. Surface roughness is a factor in friction when the materials are rough enough to cause serious abrasion. When one or more of the materials is relatively soft, much of the resistance to movement is caused by deformations or a plowing effect