Can anyone explain this case ? If a moving box is pulling with a force F and the kinetic friction is 0.4F, of course, it will move in the direction of applied force with an acceleration and the net force is 0.6F But what if the force suddenly decreases to 0.3F ? The box is still moving so the friction is still kinetic friction?? But if it is the case, then the box will slow down! This seems quite strange to me@@ Can anyone explain please?