Hi, I'm wondering what's going on when a friction force of a surface is applied to a moving block as the block slows down to zero and it, the friction force, is the only horizontal force applied. Does the friction force continue at a constant value until the last moment and just drop to 0N or is there a gradual decrease somehow? I described two scenarios below to possibly clarify what I think is not making sense. Scenario 1: Suppose I am sitting at a frictionless table and you push a block so that the block is traveling toward me at 10m/s. I am standing on the ground with normal friction. As the block approaches me, I apply force to the block with my hand at a constant force of 5N, so as to slow it down. But I continue applying the force of 5N so that the block slows down to a stop and immediately begins to speed up in the opposite direction, such that I am returning the block to its original speed in the opposite direction. Scenario 2: Suppose I push a block that is on a table, with friction, so that the block accelerates to 10m/s. When the block reaches 10m/s, I continue pushing with a force such that the net force on the block is Fnet = 0N and the velocity of the block is traveling at a constant velocity of 10m/s. Suppose I'm applying a force of 5N and the friction of the table is applying -5N on the block. The friction force is constant. Suppose all of a sudden, I immediately stop applying force to the block. The block will slow down by the force of friction from the table just as I slowed down the block with my hand in scenario 1. The difference is, in scenario 2, once the block reaches a velocity of 0m/s, it will not reverse direction and begin speeding up in the opposite direction. If the table was actually applying a constant force of -5N on the block, the block should, in theory, reverse direction and begin speeding up in the opposite direction. But instead, the table seems to stop applying a friction force of -5N just as the block reaches 0m/s. Is the friction force -5N the entire time and just disappears when the block reaches 0m/s? If I plot a Net Force .time graph of scenario 2, will I see the Net Force steadily decrease as the velocity of the block approaches 0m/s or will there be a sharp drop from 5N to 0N (maybe even an instantaneous drop) right when the block reaches 0m/s? What exactly is going on here? Thank you.