Question

what what are the two important properties of friction

Answer 1

1. It always acts in the direction opposite to the direction of motion.

2. It's magnitude is equal to that of the force trying to set the object in motion only until it starts to move. Once the object starts to move the force is constant. The former form of friction is called static friction and the latter is kinetic friction.

3. It is a non-conservative force I.e. the energy spent to overcome friction is lost to the surroundings as heat.

4. It is caused because of the irregularities on the surface of the objects. These deformities (at atomic level) on two objects interlock with each other. Since two objects cannot touch each other (Pauli's exclusion principle) they come into equilibrium due to electromagnetic forces.

5. It depends on the normal reaction between the two surfaces under consideration and also on the nature of the surfaces.

Answer 2

properties are :-
☆ It always act in the direction on opposite to the direction of motion
☆ It depends on the normal reaction between the two surface under consideration and also on the nature of surface