Can we do a tour to the great wall and terracotta warriors in an afternoon and one full day?

I am a little confused about your question. Here is my suggestion (hope I understand you correctly):
it takes around 2h by air from Beijing to Xian and the Terracotta Warriors Museum stops selling ticket around 17:00. So if you wanna visit in the afternoon upon your arrival, it is impossible. Just give it up.

To have trip for three days in Beijing and Xian, covering both the terracotta warriors and the Great Wall, I suggest you join a tour. Your travel agency would help to book the flight and attractions ticket, arrange the pick-up service and your detailed itinerary. If interested, I would recommend Travel China Guide to you. Their contact is traveltravelchinaguide.com for your reference.