Answer
The friction force on A is equal to the friction force on B.
Work Step by Step
In both situations, the force of static friction on the box is equal to the applied force and acts in the opposite direction from the applied force. Since the box stays at rest, the magnitude of the applied force and magnitude of the force of static friction must be equal. The magnitude of the force of static friction on box A is 30 N. The magnitude of the force of static friction on box B is 30 N. Therefore, the friction force on A is equal to the friction force on B.
