Here's an interesting challenge you can give to a friend. Hold a $1 (or larger!) bill by an upper corner. Have a friend prepare to pinch a lower corner, putting her fingers near but not touching the bill. Tell her to try to catch the bill when you drop it by simply closing her fingers. This seems like it should be easy, but it's not. After she sees that you have released the bill, it will take her about 0.25 s to react and close her fingers - which is not fast enough to catch the bill. How much time does it take for the bill to fall beyond her grasp? The length of a bill is 16 cm.

t <t _reaction

We see from this that the bill passes completely through the fingers before the reaction time (time without movement) passes and therefore before closing the fingers.

Explanation:

In this exercise we can use the free fall kinematics, let's calculate the time that the upper corner of the bill takes to pass through the fingers of her friend, when releasing the bill it starts with zero speed, let's use the equation

         y = v₀ t + ½ g t²

         y = ½ g t²

         t = √(2y / g)

let's calculate

         t = √ (2 0.16 / 9.8)

         t = 0.18 s

the reaction time is

         t_reaction = 0.25 s

Thus

         t <t _reaction

We see from this that the bill passes completely through the fingers before the reaction time (time without movement) passes and therefore before closing the fingers.

sleep paralysis is a parasomnia, events associated with sleep.

sleep paralysis happens when you are in the middle of waking up or falling asleep. it is the feeling of being conscious but unable to move. it definitely involves hallucinations.

i had a friend that had sleep paralysis and he told me a story one time where he was laying in bed and he couldn't move his body no matter how hard he tried and there was someone standing in the corner of his room coming towards him. he couldn't move and you can't "wake up" because you are already conscious. sometimes sleep paralysis can be triggered by frequent waking up during the night based off of multiple trips to the bathroom, or if you had ever been abused, sleep paralysis can start happening from things like that.

fgravity=10x10=100n case 1

fgravity=30x20=600n case 2

6 times more