For example, if the static friction threshold was broken but then the applied force was lowered below it, would the object keep accelerating? The question states that a force is accelerating the object to the right, does that mean static friction is irrelevant in every case? The applied force in the problem was less than the max. static friction, but once again, it was stated that "a force is accelerating the object to the right". The kinetic frictional force was well under the applied force.
Rithwik Sudharsan asked Dec 7, 2016 at 4:25 Rithwik Sudharsan Rithwik Sudharsan 73 1 1 silver badge 8 8 bronze badgesStatic friction and kinetic friction between two surfaces both involve electrostatic forces, but with different mechanisms which are complicated and are not completely understood even to this day.
However, we do know that once the static friction threshold is passed, the kinetic friction rules and the static friction mechanism is not in play in any way. If the applied force falls below the kinetic friction force, the object will start to decelerate, but due to its mechanism, the static friction force will not set up again until the object comes to a stop.
answered Dec 7, 2016 at 11:33 1,086 6 6 silver badges 10 10 bronze badges$\begingroup$ +1, good answer. Just wanted to add that 'static' friction is defined as acting only when there is no relative motion. Any friction that acts with motion is defined as part of 'kinetic'. $\endgroup$