Newton's Third Law 

Laying on your non-dominant side's hip, proceed to lube your entire hand. Next, shove entire right hand inside your anus. It is best to feel around a bit before proceeding to your left hand. Your left hand will firmly grasp your phallic member and fondle your throbbing shaft. With both of your hands in motion the force applied thus shall be performing Newton's Third Law.

Mr. Schachter: How was your night? You were screaming quite loud.

Reginald: 'Twas grand. I performed the Newton's Third Law and used an entire bottle of kY.

Newton's Third Law by One-Pump-Shotgun March 7, 2017

Newton's Third Law 

When you're running and you can feel your penis flapping around.

No dude, I don't wanna run today - newton's third law always gets me...

Newton's Third Law by flagellum_mayor January 27, 2013

Newton's Third Law of Motion 

I hit you, you hit floor.

Person 1:What is Newton's Third Law of Motion?
*Random guy punches Person 1, person 1 goes to the floor*
Person 1: OW!
Random Guy: That's the law

Newton's Third Law of Motion by Xajdyn March 27, 2013