The US Constitution - basics (video)
The link address is: https://www.khanacademy.org/humanities/ap-us-history/period-3/apush-creating-a-nation/v/the-us-constitution
The link address is: https://www.khanacademy.org/humanities/ap-us-history/period-3/apush-creating-a-nation/v/the-us-constitution