force

F=ma
in this case, F=(m+M)a
while force acting on block A by block B, f=Ma
a=F/(M+m)
so f=FM/(M+m)
so the magnitude of force force acting on block A by block B is FM/(M+m)

2007-02-22 23:18:52 補充：
just discover a mistake by remaining of garychiu_2003f should be the force acting on block B by block Aforce acting on block A by block B is 0 since there is a smooth table, no force can give the reaction force to B to make a reaction force on block A.

2007-02-22 23:18:59 補充：
so the force acting on block B by block A is FM/(M m).the force acting on block A by block B is 0

2007-02-26 21:57:17 補充：
net force of A=ma=F-the force acting on block A by block Bthe force acting on block A by block B=F-ma=(m加M)a-ma=Ma=FM/(M加m)so the force acting on block A by block B is also FM/(M加m)