Newton Balls

When a man's two testicle collide within the scrotum resulting in a painful feeling. Much like that desk toy with the swinging balls.

When you are at a sauna after working out and you are naked and start rocking hips side to side as to hit their balls together.

When guys scissor and their balls smash together

Originally an experiment demonstrating the principle of conservation of momentum, Newton's balls are five metal balls suspended in line by fine wire or string. When one ball impacts the rest, momentum is conserved and the ball at the other end is knocked into the air.
Alternatively, Newton's balls can be used to describe a sexual situation. When two men engage in anal sex in the doggy style position their balls slap together, creating an effect much like that described above. Gay people often feel that such a situation is baroque.

Where a woman gets double penetrated by 2 guys and their balls clash in the middle, essentially clacking like a set of Newtons Balls.

When three or more willing homosexuals are having simultaneous anal intercourse(like so - >>>). The furthermost partys testicles swing away gaining momentum, swings back and hits the middle partys testicles, but due to the fact that the middle partys testicles are still in contact with the foremost partys testicles, it does not move but releases the energy into the foremost parties testicles swinging them forward, thus giving the "newtons cradle" effect.

When a woman is being double penetrated and the 2 mens balls clash together, like a set of Newtons balls.