you might think im crazy but there is physics in sleeping. even though you are not doing anything much when you sleep there still is a lot happening like gravity. when you sleep gravity doesn't just turn off or else you would be floating straight into the ceiling. Gravity keeps you attached to your nice cozy bed unless you fall off your bed. then gravity take role still because it pulls you to the floor. also when you fall to the floor you have a acceleration due to gravity of 9.81 m/s^2 and you would be able to find your velocity depending on how high your bed is and how long it took for you to fall. Good thing for gravity or else you would not be able to catch any sleep!