A “K-9 cannon” uses a powerful rubber band to launch a tennis ball(mass of 0.0577 kg) vertically upwards. The tennis ball has a velocity of 25.0 m/s as it leaves the barrel. A. How long is the tennis ball in the air?

t = 5.1[s]

Explanation:

To solve this problem we must first use the following equation of kinematics.

where:

Vf = final velocity = 0

Vo = initial velocity = 25 [m/s]

g = gravity acceleration = 9.81 [m/s²]

t = time [s]

Now replacing:

Note: The key to understand this problem is that when the tennis ball is in the highest position its velocity is zero.

So it will take the same time from the highest point to the ground

t = 2.54 +2.54

t = 5.09 [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.