What is the difference between static and kinetic friction?

Static friction and kinetic friction are two different concepts that pertain to the interaction between surfaces when one object is trying to move relative to another.

Static friction is the force that must be overcome to start moving an object that is at rest. It acts on objects that are not currently in motion relative to each other, ensuring that the object remains stationary until a sufficient force is applied. Essentially, static friction acts as a barrier to motion.

On the other hand, kinetic friction comes into play once the object has started moving. It is the force that resists the motion of two surfaces sliding against each other. Kinetic friction is generally lower than static friction, which is why it can often be easier to keep an object moving than to initially start its motion.

Thus, the correct choice highlights that static friction is responsible for preventing motion, while kinetic friction is the force that resists motion once it has occurred. The distinction emphasizes the role of each type of friction under different conditions of movement or lack thereof.