Special topics of physical holistic method and isolation method The man with mass m sits on the rough horizontal table of the car with mass m. The man pulls the string around the fixed pulley with horizontal force to make the man and the car move to the right on the smooth horizontal ground with the same acceleration A. If M > m, the direction of friction between vehicle and human is to the right B. If M

Special topics of physical holistic method and isolation method The man with mass m sits on the rough horizontal table of the car with mass m. The man pulls the string around the fixed pulley with horizontal force to make the man and the car move to the right on the smooth horizontal ground with the same acceleration A. If M > m, the direction of friction between vehicle and human is to the right B. If M

First, the overall analysis, the overall force to the left by two times the pull 2T gravity support
From Newton's Law (M + m) * a = 2T, then a = 2T / (M + m)... 1, equation a is left
In order to make the human and the vehicle relatively stationary, the horizontal external force (T and friction f) on M must provide a
There are three situations
1. If the pulling force t just provides a, that is, f = 0, then t = ma and formula 1 have m = M C pairs
2. If the pulling force t is not enough to provide a, the left f is needed to have enough a, then t + F = ma, it is easy to know that mm a pair