1. Static Friction:

• Static friction is the frictional force that opposes the initiation of motion when an object is at rest and an external force is applied to it.
• It prevents stationary objects from moving until the applied force overcomes it.
• The maximum static frictional force (�static maxFstatic max​) depends on the nature of the surfaces in contact and the normal force (�N) pressing the surfaces together. The formula is often expressed as �static max=��⋅�Fstatic max​=μs​⋅N, where ��μs​ is the coefficient of static friction.
• The coefficient of static friction (��μs​) is a dimensionless constant that quantifies the stickiness of the surfaces. It varies between different materials.
• Once the applied force exceeds the maximum static frictional force, the object starts moving, and static friction is replaced by kinetic friction.

2. Kinetic Friction:

• Kinetic friction is the frictional force that opposes the relative motion between two objects that are sliding past each other.
• It acts when an object is already in motion.
• The kinetic frictional force (�kineticFkinetic​) is usually slightly weaker than the maximum static frictional force and is also proportional to the normal force (�N).
• The formula for kinetic friction is often expressed as �kinetic=��⋅�Fkinetic​=μk​⋅N, where ��μk​ is the coefficient of kinetic friction.
• Like the coefficient of static friction, the coefficient of kinetic friction (��μk​) is a dimensionless constant specific to the materials in contact.