** in problem 4.26, the coefficient of static friction between the book and the vertical back of the wagon is μs. determine an expression for the minimum acceleration of the wagon in terms of μs so that the book does not slide down. does the mass of the book matter? explain.

Explanation:

The situation is that a wagon is speeding up with a book remaining stuck with the vertical wall of the wagon . Due to acceleration of wagon , book pushes the vertical wall of wagon with some force .

Minimum acceleration be a . Acceleration of book will be a. Force on book will be ma . Reaction force R of vertical back of the wagon will be ma so friction force f  generated on the book in upward  direction will be μs x R

This friction force f will balance the weight . So

mg =  μs x R

= μs x ma

a = g / μs

Mass has no effect on this acceleration.

answer: the metamorphic rocks are formed when they are exposed to high pressure and high temperatures. this happens when one of the earth's plates comes in contact with the other plate by traveling in opposite directions, straight into each other or slipping under one another. the friction that is caused by this activity results in   melting of rocks and when it cools they are known as metamorphic rocks. this process needs a controlled amount of pressure and temperature otherwise it may turn into magma.