A person places a hand on a closed book resting on a table, and then presses downward while pushing outward. Either the book slides across the table or the hand slides across the book. What determines which of these happens? Which type(s) of friction is (are) involved?

How do static and kinetic friction play a role in this scenario? Answer: The event that occurs depends on the static friction coefficients between the book and the table (μ_sb) and between the book and the hand (μ_sh). If μ_sb is greater than or equal to μ_sh, the hand is more likely to slip on the book. If μ_sh is greater than μ_sb, it is more likely that the book slides across the table. Both static and kinetic friction are involved in this scenario. Static friction is initially present between the book and the table and the book and the hand. When either the book starts sliding across the table or the hand starts sliding across the book, kinetic friction replaces static friction at the interface where the sliding is occurring.