This site uses flash for videos. If you're having trouble enabling it, click on the information icon in the address bar to change your settings to allow Flash.

# Exponential Decay (Half-Life) $A_t=A_0(\frac{1}{2})^\frac{t}{h}$

- 1Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ A radioactive substance has a half-life of 3 hours. If you start with 100 g, what mass will remain after 12 hours?

(Note: This lesson includes a brief explanation of half-life.) - 2Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ A radioactive substance has a half-life of 18 hours. If you start with 18 g, what mass will remain after 3 days?
- 3Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ A radioactive substance has a half-life of 15 hours. If you start with 100 kg, what mass will remain after 2 days?
- 4Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ A radioactive substance has a half-life of 20 hours. How long will it take for 400g to decay to 50g?
- 5Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ A radioactive substance has a half-life of 7 hours. How long will it take for 768g to decay to 24g?
- 6Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ A radioactive substance has a half-life of 5 days. How long will it take for 1312 kg to decay to 82 kg?
- 7Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ If you have 68g of a radioactive substance that decays to 17g after 12 days, what is the half-life?
- 8Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ If you have 192g of a radioactive substance that decays to 3g after 18 years, what is the half-life?
- 9Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ A radioactive substance decays to $\frac{1}{16}$ of its original amount after 24 days. What is the half-life? $$ $$ Good test question!
- 10Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ A radioactive substance decays to $\frac{1}{32}$ of its original amount after 15 days. What is the half-life? $$ $$
- 11Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ How long will it take for a radioactive substance to decay to $\frac{1}{4}$ of its original amount, if the half-life is 40 minutes?
- 12Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ How long will it take for a radioactive substance to decay to 25% of its original amount, if the half-life is 5 days? $$ $$ Good test question!
- 13Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ How long will it take for a radioactive substance to decay to 12.5% of its original amount, if the half-life is 9 days?
- 14Use the equation $A_t=A_0(\frac{1}{2})^\frac{t}{h}$ to solve. $$ $$ What is the half-life of a radioactive substance if it decays to 6.25% of its original amount after 32 minutes?

$$e=mc^2$$