Thanks for posting your query at HealthCareMagic. The condition that you are reporting has been caused by dysfunction of the vestibulo-cochlear apparatus. I do not think that any concussion has occurred. Let me explain in further detail. There is a vestibulo-cochlear apparatus in our inner ear which is responsible for maintaining our balance. This gives the sense when we get up from lying position or when we turn our head. When the child got into the roller coaster, the vestibulo-cochlear apparatus was bombarded with stimulus which it had not faced earlier. As a result it could not decide whether the body is in upright or reclining position and got confused. The dizziness has resulted from this. Some stabliser of the vestibulo-cochlear apparatus can provide him relief. You may give him Stemetil tablets. Since I do not know his age and weight, I would not be able to give you the exact dose he requires. Get in touch with your pediatrician and he will guide you. Hope that helps. Feel free to revert back in case of further queries if any.