Question

What amount of plutonuim would be left after 5000 years if you initially have 14 kilo- grams? The half-life of plutonium 240 is 6500 years.

Answer 1

`sf(8.2color(white)(x)"kg")`

Explanation:

`sf(M_t=M_0e^(-lambdat)`

`:.` `sf(lnM_t=lnM_0-lambdat)`

`sf(lambda=0.693/t_(1/2)=0.693/6500=1.066xx10^(-4)color(white)(x)a^(-1)`

So:

`sf(lnM_t=ln14-(1.066xx10^(-4)xx5000)=2.64-0.533=2.107)`

From which:

`sf(M_t=8.2color(white)(x)kg)`