When we push an object on the surface, if I push hard enough such that it reach the maxium static friction of the object then it start moving with a constant speed and F_push = F_friction. But when I realease the object F_push immediately become zero remain only F_friction. Does the friction get smaller to static friction when the object velocity become 0 and stop moving? Why it getting smaller?, it don't behave like f_push while f_push is executed immediately after I release the object. Is there a case where the friction decrease the velocity of the object and make it moving backward?