An expensive wine glass is hit by a spoon. a sound with a dominant frequency of 500 hz can be heard. according to simplified calculations which ignore friction a frequency of 502 hz is expected. the glass will break, if the oscillation amplitude exceeds 2 mm. calculate which amplitude due to an external excitation is required at the resonance frequency to break it.

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.