27. each piston of an engine makes a sharp sound every other revolution of the engine. (a) how fast is a race car going if its eight-cylinder engine emits a sound of frequency 750 hz, given that the engine makes 2000 revolutions per kilometer? (b) at how many revolutions per minute is the engine rotating?

a)V= 93.75 m/s

b)The number of revolution per minute = 11,250 rev/min

Explanation:

Given that

Number piston , n =8

 Frequency ,f= 750 Hz

Revolution(R) = 2000 revolutions per kilometer

frequency of each piston

f'=f/n

f'=750/8

f'=93.75 Hz

So the number of revolution made by piston(r) = 2 x 93.75 rev/s

number of revolution made by piston(r) = 187.5 rev/s

The number of revolution per minute = 187.5 x 60 rev/min

The number of revolution per minute = 11,250 rev/min

So the speed of car V given as

r =number of revolution per second

R = revolutions per kilometer

V= 93.75 m/s

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.

it takes about 30 days for it to break down