Arock is thrown upward from the top of a 30 m building with a velocity of 5 m/s. determine its velocity (a) when it falls back past its original point, (b) when it is 15 m above the street, and (c) just before it hits the street. a horse drags a 100 kg sled a distance of 4 km in 20 minutes. the horse exerts one horsepower, of course. what is the coefficient of sliding friction between the sled and the ground?

a) 5 m/s

b) 17.8542 m/s

c) 24.7212 m/s

0.229

Explanation:

t = Time taken

u = Initial velocity = 5 m/s

v = Final velocity

s = Displacement

a = Acceleration due to gravity = 9.81 m/s²

So, the stone would travel 1.27 m up

Velocity as the rock passes through the original point is 5 m/s

Time taken to reach the original point is 0.51+0.51 = 1.02 seconds

So, total height of the rock would fall is 30+1.27 = 31.27 m

Time taken by the stone to reach 15 m above the ground is 1.82+0.51 = 2.33 seconds

Speed of the ball at 15 m above the ground is 17.8542 m/s

Speed of the stone just before it hits the street is 24.7212 m/s

F = Force

m = Mass = 100 kg

g = Acceleration due to gravity = 9.81 m/s²

s = Displacement = 4 km = 4000 m

P = Power = 1 hp = 745.7 Watt

t = Time taken = 20 minutes = 1200 seconds

μ = Coefficient of sliding friction

F = μ×m×g

⇒F = μ×100×9.81

W = Work done = F×s

P = Work done / Time

⇒P = F×s / t

Coefficient of sliding friction is 0.229

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.