Thread: Exponential Growth and Decay

Hi, This is my first post, i couldn't find a proper category for my topic, so I'll post it here. having troubles understanding these questions...

I have attached the two questions... thanks. They use the Q = Qo*e^kt and Q = Qo*e^-kt formula structures. Thank you very much in advance.

For your equation



Substitute the points and

What do you get?

Originally Posted by pickslides

For your equation



Substitute the points and

What do you get?

um sorry? where did you get points from? I've never been taught to get points for these questions?

I found these points from you question.

At t=0 the amount of radioactive material is , is this clear why?

Now the meaning of half life is the time taken for the radioactive material to reduced to half of its original self.

From the question, when t=1600 then the initial amount is halved i.e

Originally Posted by pickslides

I found these points from you question.

At t=0 the amount of radioactive material is , is this clear why?

Now the meaning of half life is the time taken for the radioactive material to reduced to half of its original self.

From the question, when t=1600 then the initial amount is halved i.e

ohk, makes sense now, will give it a try. thanks

Originally Posted by MathsBeforeBedtime

ohk, makes sense now, will give it a try. thanks

Good to hear, let us know how you go.

Originally Posted by pickslides

Good to hear, let us know how you go.

turns out I didn't get it. my tutor said for part a), do 500 / 1600 to get 0.3125 = 31%, then just do 50% - 31% = 19%

for part b) my tutor said to go from 100% to 50% that's a half life so it = 1600 years, then to go from 50 to 25% that's another 1600 years and so now we are at 75%. 1600 + 1600 = 3600 years.

turns out you didn't need to use the formula for this question, bit weird. but makes kinda sense this way.

qs 14 I do not know.