Final answer:
Static friction applies when objects are not moving relative to each other. Overcoming static friction requires more force than maintaining movement against kinetic friction.
Step-by-step explanation:
The primary difference between static friction and kinetic friction lies in whether objects are at rest or in motion. Static friction acts between objects that are not moving relative to each other and is generally greater than kinetic friction because it compensates for the forces acting to initiate movement. Kinetic friction, on the other hand, occurs once the objects are already sliding past one another and is typically less than static friction, which results in less force needed to maintain motion than to start it.
For example, when trying to slide a heavy crate across a floor, you encounter static friction initially. You have to exert enough force to overcome this static friction for the crate to start moving. Once it starts to move, the force of friction you need to overcome drops to the level of kinetic friction, which is lower, making it easier to keep the crate sliding on the surface.