Two swimmers relax close together on air mattresses in a pool. one swimmer's mass is 48 kg,
and the other's mass is 55 kg. if the swimmers push away from each other,
a. their total momentum triples.
b. their momenta are equal but opposite.
c. their total momentum doubles.
d. their total momentum decreases.

B. their momenta are equal but opposite.

Explanation:

For the law of conservation of momentum, the total momentum of an isolated system is conserved.

If we consider the two swimmers as an isolated system, their total momentum is given by:

At the beginning, they are both relaxing, so they are at rest; therefore their total momentum is zero:

p = 0

Later, they push each other. According to Newton's third law of motion, they push each other with the same force (action-reaction pair), so the change in momentum of each swimmer will be equal to that of the other swimmer (in magnitude), according to

where F is the force applied and the duration of the collision.

Since they amount of momentum they gain is the same (in magnitude), but they both started with zero momentum, than this means that their final momenta have same magnitude; and also, they have opposite direction, since they pushed in opposite directions.

So, the correct answer is

B. their momenta are equal but opposite.

found in the nucleus

has mass of one amu

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.