Acceleration between two frames

[vela]

Both diagrams are wrong. You made the same mistake earlier in the thread.

I haven't studied physics since 2010 and that was just basic stuff, so anything I think is correct is probably not. Anyway, I hope the below is correct.

We all make mistakes, so it's important to develop the ability to check your work and find those mistakes. For example, when you drew the first diagram, you could have also written down the equation it represents by interpreting the diagram. Then you would have hopefully seen the subscripts were messed up and realized the diagram had a problem. By getting in the habit of looking at the same concept in different ways, you'll start to see how they all fit together.

View attachment 291185

The second diagram is still wrong.

 

[Monsterboy]

The second diagram is still wrong.

Ok, when I tried parallelogram, I figured I was putting $-\vec{a}_{P, S2}$ on the wrong side.

This must be right.

 

[vela]

That's right.

 

[Monsterboy]

Thanks all, for the support!