Final answer:
Adding mass on a wooden block increases both the static and kinetic coefficients of friction only by increasing the normal force. The inherent properties of μs and μk are not changed by the addition of mass. The experiment to find μk using a tilted book introduces some uncertainty due to the nature of static and kinetic friction differences.
Step-by-step explanation:
When a standard mass is placed on top of a wooden block, both the coefficient of static friction (μs) and the coefficient of kinetic friction (μk) will generally increase. This is because adding mass increases the normal force (μs and μk are proportional to the normal force exerted by the surface). However, the actual values of μs and μk do not change; rather, the frictional forces increase because they are the product of the coefficients and the increased normal force.
Experiments like tilting a book to measure the angle at which a coin starts to slide help determine the coefficient of kinetic friction (μk). If you need to measure the angle of tilt relative to the horizontal to find μk, remember that μk is inherently lower than μs, which means the coin won't move until a certain tilt angle is reached, creating some uncertainty in the measurement of μk.