m=Me^kt
M=25
t=10
how can i possibly work out m if i don't know k? the question asks this....
'a particular radioactive substance modelled by equation m=Me^kt has a half life of 6 years. if initially the amount present , M, is 25grams, how much would remain after 10 years'
m=Me^kt
1/2=e^kt
1/2=e^6k
k=ln(1/2) / (6)
k=-0.11552.......
m=Me^kt
m=25e^(-.11552*10)
m=25 x .314980
m=7.87450 grams- amount remaining after 10 years.
P.S. YOU CAN USE A MUCH SIMPLER METHOD TO GET THE SAME ANSWER AS FOLLOWS:
10/6=1.666667 half-lives elapsed after 10 years.
m=25 x 2^-1.666667
m=25 x .314980
m=7.87450 grams- amount remaining after 10 years.
YOU MAY BRING IT TO THE ATTENTION OF YOUR TEACHER.
+37170 7.875 gms HINT: Use the half life as 6 yrs to calculate k = -.11
m=Me^kt
1/2=e^kt
1/2=e^6k
k=ln(1/2) / (6)
k=-0.11552.......
m=Me^kt
m=25e^(-.11552*10)
m=25 x .314980
m=7.87450 grams- amount remaining after 10 years.
P.S. YOU CAN USE A MUCH SIMPLER METHOD TO GET THE SAME ANSWER AS FOLLOWS:
10/6=1.666667 half-lives elapsed after 10 years.
m=25 x 2^-1.666667
m=25 x .314980
m=7.87450 grams- amount remaining after 10 years.
YOU MAY BRING IT TO THE ATTENTION OF YOUR TEACHER.
