She is 'racing against the clock' to be sure the assignment is handed in on time.
Her mind was 'racing'. [=she had many thoughts going quickly through her mind]
Researchers are 'racing (against time)' to find a cure.
(..) - Great. I'm gonna go get it. I'm gonna... I can't tell you how excited I am! This is gonna be such a lift! My heart is just racing right now! I'm gonna get it, and I'll be back. Whoa, whoa, Gil! Take it easy! You had a big night. Fitzgerald. Hemingway! (..)2011 Midnight in Paris