Question

suppose sally wants to push a couch across the room. explain how static friction and sliding friction are both involved in this process.

Explanation:

Static friction resists the start of motion. When Sally tries to push the stationary couch, static friction acts between the couch - floor interface to oppose the applied force. Once the applied force exceeds the maximum static friction, the couch starts to move. Then sliding friction takes over, which is generally less than the maximum static friction and acts to oppose the continued motion of the couch.

Answer:

Static friction initially resists the couch from moving when Sally applies a force. Once the force exceeds the maximum static - friction value, the couch starts moving and sliding friction then acts to oppose its motion.