Radioactive Half-Lives

1) The graph above is from student data collected during the penny flipping lab. The student began with 150 pennies. After approximately how many flips were there only half that many pennies remaining?

2) Find 70 pennies on the decay curve. How many flips before there are approximately half that many pennies remaining?

3) What is the half life, in “flips”?

4) This questions has two parts. Using the graph above, at what time are there 30 grams remaining? At what time are there 15 grams remaining?

5) Using your answers from Question 4, subtract the large time from the smaller time, and write your answer below. This is the half life.

6) Now that you know the half life, you’ll need it to answer these questions. If you started with 1000 grams of this material, how much would remain after 20 seconds?

7) Using the same half life, how much would remain after 40 seconds?

8) Find the half life for the decay curve above.

9) Start with 50 grams. How much time will pass before 15 grams remain?

10) Start with 84 grams. How much time will pass before 42 grams remain?

11) If you started with 150 grams, how much time would pass before there were 75 grams remaining?

12) If you started with 400 grams, how many half lives would pass before there were 100 grams left? How many years is that?