Rewrite using commas.

When you balance on a skateboard there are three forces at work.

I wrote...
When you balance on a skateboard, there are three forces at work.

Yes.

Thank you

Your rewrite, "When you balance on a skateboard, there are three forces at work," correctly uses commas to indicate a pause in the sentence. Commas are used in this case to separate the introductory phrase "When you balance on a skateboard" from the main clause "there are three forces at work." This helps to clarify the sentence structure and improve readability. Well done!