Nothing is wrong with your question, but the site has a superhard policy against homework tasks. It is applied so strictly, that even a lot of questions obviously not being homework problems are closed on this reason.
In the current state of your question, there is not too much to do, because the majority of the voters doesn't want it.
However, the homework close reason says this:
"Homework-like questions should ask about a specific physics concept and show some effort to work through the problem."
So, re-formulate it to ask about a specific physics concept, and show some effort.
The funny thing is: probably your question will be still closed or left closed. What I would do: Make clear, that you have both, best if you insert a short excerpt of both in the beginning of the post.2 So:
- Specific physics concept: I see a contradiction here, on Newton II law the force on the chair should be [..]
- My effort: As we can see it in the second half of the post, ...
[and here is your question]
It is very likely, that your question will be still closed. But, on this way, you will have already enough ammunition to start this meta discussion.
You will get many critics, questions and suggestions in the comments. Do everything what they say, even if they seem irrelevant or hairsplitting for you, it helps a lot in their voting1. This is your only defense against negative votes: react comments quickly, and do it with quick and convincing comments and edits.
If someone explains the reason of the negative vote (down or close) to your post, honor it: nothing makes it obligatory to give a reason for a vote.
Unfortunately, following all of these makes asking a homework question actually harder than solving it for yourself.
The community consent is very strongly against numerical problems here, there is only an admittedly very narrow "escape path" from this, which is mainly closed despite that it is communicated as if it would be open.
Your current question is already closed, and getting the 3 reopen votes is possible, but unlikely.
1 My heuristic (unproovable, but for me realistic) estimation is that for every comment, there are around 2-3 people, who doesn't comment, only votes. And there are around 10 people, who doesn't even vote, but thinks the same. Any time if you get a comment to your post, imagine average 2-3 people who votes the same and 10 other who thinks the same. And voters typically don't come back to reconsider their vote, this is why you need to react quickly.
2 The first sentences create a general impression in the reviewers (and any readers), what is your post about. The rest will be interpreted already in this frame. Thus, your first sentences are super-important.