This babe's got all the momentum of a Newton's cradle (also known as the "clicky-clacky desk thing"). See the illustration: after her hand slides down a cock, on the other side her tongue slides up into a mouth. We don't even need to see formulas and solutions accounting for friction and heat; we'll just accept this as is. Could we please have her and this strapping young stud set atop our desk? We'd wile away the hours watching their back-and-forth motion. But then we probably wouldn't get any work done. Maybe it's not a good idea... But it would make a great gift!
[Via NSFW GIF. Have a GIF you'd like to see us feature? Email us!]