A rock sample contains 1/4 micrograms of the parent radioactive ...

[OSWALD]

A rock sample contains 1/4 micrograms of the parent radioactive isotope K-40 and 3/4 micrograms of its daughter isotope Ar-40. If the half-life of this decay is 1.25 billion years, how old is this rock?
 
  A) 5.00 billion years
  B) 3.75 billion years
  C) 1.25 billion years
  D) 2.50 billion years

Question 2

Starting from rest, a proton falls through a potential difference of 1.2 kV. What speed does it acquire?
 
  What will be an ideal response?

[kardosa007]

Answer to Question 1

D

Answer to Question 2

4.8  105 m/s

[OSWALD]

Thanks for the timely response, appreciate it

[smrtceo]

Wow, this really help