# Homework Help: Just a physics problem

1. May 14, 2004

### mustang

Problem 18. A sample of organic material is found to contain 19 g of carbon. Based on samples of pottery found at the site, investigators believe the material is about 22922 years old.
Estimate what percentage of the material's carbon-14 has decayed. Answer in units of %.
Note; How do you do this problem?

2. May 14, 2004

### HallsofIvy

The first thing you do is look up the "half-life" of carbon-14. It's probably in your text book, I'll call it "H" here. If T= H, then 1/2 or 50% of the carbon-14 has decayed. If T= 2H, then (1/2)2= 1/4 is left so 3/4 has decayed. If T= 3H, then (1/2)3 has decayed. How many times does the half-life of carbon 14 divide into 22922? (include decimal places). What is 1/2 to that power? That's how much is left. Once you know that, subtract from 1 to find what part has decayed.

3. May 14, 2004

### mustang

I figured it out.

Thanks! I did what you said and got 93.8
degrees.

4. May 16, 2004

### HallsofIvy

I do hope you meant "percent" rather than "degrees"!