nuclear and radioactivity, textbook question?

Question

A radiation source delivers a dose of 10 Gy on a target of mass 3.0 g during a 14-minute interval. Every disintegration delivers on average 70 MeV to the target. Assume the activity of the source is constant during the time involved.
a) Determine the power output of the source
b) What is the activity of the source?

I don't just want the answer, please explain it too, thanks a lot.

Answer 1

Power is amount of energy delivered per a time interval
P=E/t
Also
1 rad = 0.01 gray (Gy) = 0.01 joule of energy absorbed per kilogram of matter

a)
E= 10Gy (3E-3 kg)=3E-2 Joules
P=E/t=3E-2/(14 x 60)=3.57E-5 watts

b) 1 eV = 1.602 x 10-19 joules
E=70 E6 x 1.602 x 10-19 =11.2E-12 Joules
P=11.2E-12 /(14 x 60)= 13.35 E-15 Watts

Answer 2

i'm no longer precisely confident what you have have been given there, yet you elect the mass for the right isotope of lead that's the manufactured from the beta decay.  this is going to be distinctive from the conventional atomic mass of organic lead, which is composed of countless reliable isotopes. additionally, you may desire to subtract the mass of the electron from the products of the beta emission to get the means of the product debris (the electron and the antineutrino).  The mass of the electron is around 511 keV, if memory serves.