Newton's Laws and Force Problem

[Yosty22]

Homework Statement

A student tries to raise a chain consisting of three identical links. Each link has a mass of 380g. The three-piece chain is connected to a string and then suspended vertically, with the student holding the upper end of the string and pulling upward. Because of the student's pull, an upward force of 12N is applied to the chain by the string. Use Newton's laws to answer the following questions.
a). Find the acceleration of the chain.
b). Find the force exerted by the top link on the middle link.

Homework Equations

F=ma
F_A on B= -F_B on A

The Attempt at a Solution

I can't for the life of me figure out letter b. For a), I did:
T-mg=ma
12-(.380*3)(9.8)=(0.380*3)a
Solve for a, get:
acceleration = 0.726 meters per second squared.
This is the correct answer. However, I have no idea at all how to set up or solve part B.

 

[SammyS]

Homework Statement

A student tries to raise a chain consisting of three identical links. Each link has a mass of 380g. The three-piece chain is connected to a string and then suspended vertically, with the student holding the upper end of the string and pulling upward. Because of the student's pull, an upward force of 12N is applied to the chain by the string. Use Newton's laws to answer the following questions.
a). Find the acceleration of the chain.
b). Find the force exerted by the top link on the middle link.

Homework Equations

F=ma
F_A on B= -F_B on A

The Attempt at a Solution

I can't for the life of me figure out letter b. For a), I did:
T-mg=ma
12-(.380*3)(9.8)=(0.380*3)a
Solve for a, get:
acceleration = 0.726 meters per second squared.
This is the correct answer. However, I have no idea at all how to set up or solve part B.

Draw a Free Body Diagram for the bottom link.

Draw a Free Body Diagram for the middle link. (Maybe this one is all you need.)

Draw a Free Body Diagram for the top link.