Author: Gilove2dance Title: Calculations Prompt #35-Speed of rayne_shippers’ mini challenge table created by bugchicklv Rating: G Pairings: Rayne in all its godliness Disclaimer: Joss is boss; I’m just a lowly minion. Word count: 501 Author's notes: Grade 12 Physics has corrupted my brain. But I liked the idea of Jayne trying to understand something way beyond his knowledge just to make River happy.

~*~*~ “Whatcha doin’, Crazy?” Jayne walked into the cargo bay to find River by the wall, fixing a crate full of a dull grey clay to the ceiling.

“An experiment.” She tied off the knot and reached down to the ground for a roll of tape and chalk. She taped the chalk to the bottom of the crate so that it was touching the wall of the cargo bay.

“Whatcha experimentin’ on?” He looked at the crate was curiosity.

“I wish to find out the velocity of my gun.” River patted the new gun at her hip. It was her birthday gift from him, a shiny Sauer P220 pistol.

“What fer?”

“So that I can calculate the trajectory and range when we are jobs. The only way to do that is to have the knowledge of the velocity of the bullet which is different for every single gun. The only way to obtain this information is to perform an experiment.” Satisfied that the chalk was in position, River walked away from the crate, counting her paces, to where Jayne’s weight bench, a pad of paper and a pencil where. She scribbled something down.

“An’ a crate full of clay will do that?” Jayne sounded impressed. He walked up behind her and wrapped his arms around her waist, chin resting on her shoulder.

“With the correct measurements, yes. It will act as a ballistic pendulum. When I shoot the gun, the bullet will travel into the clay, causing the crate to swing back. The chalk will draw on arch, showing how high it went. With the difference of height, I can use the gravitation energy formula, which equals the kinetic energy formula of the crate just as the bullet hits it, to calculate the velocity of the crate and bullet.

“Using the theory of momentum, where the initial momentum equals the final momentum, I can calculate the initial velocity of the bullet. It is a simple matter of working backwards until the correct variable is found.” River sketched all this out on her paper.

“I was never good at schoolin’. Teacher always said I was to distractin’.” Jayne kissed the side of her neck, working his way up to her ear. She shivered and turned around in his arms.

“You are definitely a good distraction,” she murmured and then pressed her lips to his. He responded by drawing her closer to him.

She broke off the kiss but remained close to him. They stayed there several minutes, just breathing together. River reached up and brushed his lips with her fingernails. Jayne shuddered and gripped her wrist.

“If ya continue like that, you ain’t gonna finish yer experiment,” he rumbled. She laughed softly and kissed him. Jayne pushed her away after a long moment. “Go on. I wanna see ya find that speed.”

As River walked to her position and readied her gun, Jayne whispered, “It prolly ain’t as fast as my heart is racin’.” He shook his head and smiled at his girl.