What should I do to make it upvoted? Was I not clear in the question or what is it? I haven't particularly asked help in calculations or doing questions just as to why one line of thinking is wrong...
Maybe certain users view it as a kind of "check my work problem" (I view it this way, hence my vote to close). You are asking others to check the work you are doing and compare it to / check the work done by someone else as well.
Also some users are very quick to down vote a question that involves a simple mechanics exercise thinking that a user is just looking for homework help.
Note that I'm not saying that either of these things are your intention, just giving a possible explanation for the down votes.
This is a typical check-my-work problem that IMO is not terribly interesting beyond answering a specific question by the OP.
I didn’t downvote the question, but I did vote to close: there’s nothing intrinsically wrong with the question but I do think if people ask too many questions of this type the site will become a homework help site and will lose its appeal.