The ages of rocks that contain fossils can be determined using the isotope 87rb. this isotope of rubidium undergoes beta decay with a half‑life of 4.75×1010y . ancient samples contain a ratio of 87sr to rb87 of 0.0125. given that 87sr is a stable product of the beta decay of 87rb, and assuming there was originally no 87sr present in the rocks, calculate the age of the rock sample. assume that the decay rate is constant over the relatively short lifetime of the rock compared to the half-life of 87rb.

The age of the rock is years

Explanation:

We can write the formula for the quantity of material in an exponential decay as:

where is the initial quantity of the material, and is the mean lifetime of the material.

This means that the total material that has decayed is:

The mean lifetime can be obtained from the half-life ( ) by the relationship

For our problem, as there was no Sr-87 present in the rock initially, and its a product of the decay,  its abundance will be given by , this means, the total quantity of material that has decayed.

So, our equation for the ratio will be

Working it a little

The half-life of the problem is

So, the age of the rock will be

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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.

i really dont know but i will try okay.

so i think u would just add all them up and get your answer..