Answer:
maximum static frictional force of the wall on the book (Increasing)
normal force of the wall on the book (Decreasing)
weight of the book (Not changing)
Explanation:
Now according to Newton's third law of motion
"Every action has equal but opposite reaction"
By the data given in question, Albert was pressing the book against the wall.Now, Albert started to reduce his force up against the wall.
First we have to consider all the forces applied on book in this scenario.
1. Weight of book acting downwards (y-axis)
2. Friction between book and wall acting upward (y-axis)
3. Albert's force on book against wall (x-axis)
4. Normal reaction of wall against Albert's force (x-axis)
Now, when Albert reduced his force, new scenario will be
1. Weight will be remain constant as it is W = mg
Neither mass nor acceleration due to gravity changed, so weight acting upon the book will remain same.
2. When Albert reduced force, normal reaction of wall reduced against it according to Newton's third law of motion
3. Now notice that friction is a force which acts in accordance with the applied force. For example if a box is placed at floor, no friction is applied, but when you drag the box, friction starts to act and increases until its limit comes. So, when Albert reduced his force, weight will try to pull the book and maximum static friction will increase to hinder the movement of book downwards.
Notice that maximum static friction will hinder the book from movement, since Albert reduced his force, but wight didn't pull the book, which means that maximum static friction increased to hinder downward motion.
(length of a tennis court)