I am trying to self learn kinematics , but i don't understand a certain concept :- If a string hold a mass which in turn holds another mass by a string. by F.B.D to in forming the first equation , we take T1 = m1g +t2 but shouldn't the second mass be included as well. eg. if we are hanging something with a thread and someone hangs another string and mass to it , the strain on the first string is increases . I am sorry for the vague outline i could give , hope you can understand it .