Both viscosity and friction that oppose relative motion, arise from intermolecular forces and depend on the nature of surfaces in contact.
Which of the following is/are true about frictional force?
1. It depends on the nature of the surface in contact.
2. It always opposes relative motion between two objects.
3. It is a contact force.
4. It is a non- contact force.
Friction is a force which opposes relative motion between two surfaces in contact with each other.