# Homework Help: Nuclear physics question

1. Apr 12, 2007

### GTBuzz42

1. The problem statement, all variables and given/known data
A sample of radioactive isotope is found to
have an activity of 120 Bq imediately after it
is pulled from the reactor that formed the iso-
tope. Its activity 1 h 55 min later is measured
to be 85.8 Bq.
Find the decay constant of the sample. An-
swer in units of h^-1.

2. Relevant equations

1Bq= 1 decay/sec ln(2)/k= t(half-life)

3. The attempt at a solution

120-85.8/(115*60)?

2. Apr 12, 2007

### Dick

Not even close. You'll also want the equation that B0*exp(-k*t)=B1, where B0 in the initial activity, B1 is the final activity, t is the time elapsed and k is the decay constant.

3. Apr 12, 2007

### GTBuzz42

Then the half life should just be ln(2)/lambda?

4. Apr 12, 2007

### Dick

That's what you've already said, isn't it? Except for some reason you switched k to lambda.

5. Apr 12, 2007

### GTBuzz42

thanks

If I have solved for a Coulomb force between an alpha particle and a carbon nucleus, is there any relations that get to potential energy? I thought energy from that would just be Fr

6. Apr 12, 2007

### Dick

That's pretty vague.