A box is resting on the floor. To move it, a (variable) force is applied as shown in the diagram below. Give the (likely) value of the force of limiting friction.

The box begins to move when a force of '3F' is applied, but not when a force of '2F' or 'F' is applied, indicating that the limiting friction in this situation is '3F'. The applied force must reach a certain point before it exceeds the limiting friction or maximum static friction, which is represented by the force "3F." Therefore, "3F" represents the limiting friction value.

A box is resting on the floor. To move it, a (variable) force is applied as shown in the diagram below. Why does the box stay at rest in the cases corresponding to Fig (a) and Fig (b)?

Due to static friction, the box remains at rest in situations when forces 'F' and '2F' exist. The static friction between the box and the floor is sufficient to stop the box from moving when a force of 'F' and "2F" is applied because static friction is still larger than the applied force. Until an external force (in this case, '3F') is strong enough to overcome the static friction's resistance, static friction maintains the box at rest. The box begins to move once the applied force exceeds the maximum static friction. So, the box stay at rest when force F and 2F exist and starts motion when force 3F exist.

A box is resting on the floor. To move it, a (variable) force is applied as shown in the diagram below. Mark the direction of frictional force, and mention the kind of frictional force that comes into play, in each case.

The direction of frictional force and the type of frictional force present in each situation are as follows:- 1. When a force 'F' is applied, yet the box does not move:- The direction of frictional force: The frictional force acts in the opposite direction of the applied force "F,". The force attempting to move the box forward is resisted by it. Kind of frictional force: Static friction is a type of frictional force that is present. As long as the applied force 'F' is insufficient to overcome the resistance of the static friction, the box cannot move because of static friction. 2. When a force '2F' is applied, yet the box does not move:- The direction of frictional force: The frictional force acts in the opposite direction of the applied force "2F,". The force attempting to move the box forward is resisted by it. Kind of frictional force: Static friction is a type of frictional force that is present. The applied force '2F' is insufficient to overcome the static friction, hence the static friction is still powerful enough to keep the box from moving. 3. When a force '3F' is applied and the box moves:- The direction of frictional force: The frictional force acts in the opposite direction of the applied force "3F,". But it is no longer powerful enough to prevent the box from moving forward. Kind of frictional force: The applied force, "3F," is initially opposed by static friction, but the box begins to move when the applied force exceeds the maximum static friction. When the box is moving, the frictional force involved shifts from static friction to kinetic friction, which reduces resistance to motion.