Part 2

P34 What is the strength of the basic force?

P37 The tension at the ends of Microelementdsshould be understood as the force can be changed. (Think as function. )

This topic has been thinking for a while: Why can the tension that reverses at any point on the cylinder generate pressure and can generate friction?I figured it out later: Should analyze the force of an arc(The relationship between Infinitesimal and zero)

P42 Integral operation of Expression(4) of Example2

free C calculation. But The upper and lower limits of the points must correspond, so that makes sense

P43 One of the principles of the governor

Interesting！！！

P44 Explain the necessary and necessary questions when Vector equation decomposition into scalar equation

In fact, it is such a problem: $f(x)i + g(y)j = 0$

P45 Viscous drag of an object moving in a fluid

Interesting！！！

P50 Introduction of the concept of centrifugal force