The half life of cobalt is 5.27 years. If 100 grams of radioactive cobalt is present now, how much will be present in 20 and 40 years. Find the constant and then the 20 and 40 years. Noe^kt

Question

The half life of cobalt is 5.27 years. If 100 grams of radioactive cobalt is present now, how much will be present in 20 and 40 years.  Find the constant and then the 20 and 40 years.  Noe^kt

campbell_st · Answer

ok... this is exponetial decay

half life means that the 100 gm reduces to 50 g and as a result you will be able to find the constant of decay

$$50 = 100e^{k \times 5.27}$$

you need to solve this equation for k

amtran_bus · Answer

The constant is -0.132

campbell_st · Answer

yep... thats well done so now your equation is 

$$N = 100e^{-0.132 \times t}$$

substitute your t values t = 20 and then t = 40 to find the respective weights of cobalt

amtran_bus · Answer

20 yrs= 7.136g
40yrs= .509g

campbell_st · Answer

yep that looks correct... well done

amtran_bus · Answer

God bless.