Find tension between blocks 2 & 3

[Rey4312]

Homework Statement

There are three blocks connected by strings as shown in the figure. Each block has the mass as following mass,
m1=0.8kg
m2=2.2kg
m3=1.7kg
Assuming there is no friction,

Homework Equations

F=MA

The Attempt at a Solution

In my FBD of the hanging box
\uparrow <--- Tension
[]
\downarrow <--- W=mg

^^ in y direction: T-W=0
T=W

The FBD of the box on the table
\uparrow <---Normal Force
[] \rightarrow <--- Tension
\downarrow <--- W=mg

^^ x direction: t=0
y direction: Fn-W=O

But I am completely confused on how to find the tension of the boxes

 

[tiny-tim]

Welcome to PF!

Hi Rey4312! Welcome to PF!

Call the tensions "T₁" and "T₂", and the acceleration "a" (it'll be the same for all three boxes, won't it? )

Then do F = ma three times, once for each box, and solve …

what do you get? ​

 

[Rey4312]

But if i do that the acceleration = 0 and so it makes all the forces 0... right??or am i missing something and it should be gravity?

 

[tiny-tim]

Yes, you need to include W (=mg) for the hanging box.

 

[Rey4312]

W for the hanging box is 16.66

and W for box 2(m2) is 21.56...

Where do i go from there, because that doesn't give me acceleration...

 

[Rey4312]

i figured it out... i ended up having to do m2a+m1a