Engineering Dynamics, weight is missing, simple problem

[bigu01]

Homework Statement

It is given in the photo

Homework Equations

They are all given in the photo

The Attempt at a Solution

I solved exactly the same as in the solution manual, except for the FBD of the slider B, when they write the 2nd Law, they do not input the weight there, only the Tension force by the rod.Why did they do that, that was the part I did not understand. Note: For the B block they use the x-direction as vertical.

 

[PhanthomJay]

Homework Statement

It is given in the photo

Homework Equations

They are all given in the photo

The Attempt at a Solution

I solved exactly the same as in the solution manual, except for the FBD of the slider B, when they write the 2nd Law, they do not input the weight there, only the Tension force by the rod.Why did they do that, that was the part I did not understand. Note: For the B block they use the x-direction as vertical.

good question, they forgot to include the weight of the block B in the free body diagram. In fact, they didn't include the weight of block A in its free body diagram, although that doesn't affect the solution. But the omission of block B weight was an apparent oversight that does affect the result.

 

[AlephZero]

The sliders move with negligible friction in the horizontal slots shown.

The picture is a top view. The mass of both blocks is relevant, but their weights are not.