The half-life of cobalt is 5.26 years. if 10 grams are left after 15.78 years, how many grams were in the original sample?

Explanation:

This problem can be solved using the Radioactive Half Life Formula:

  (1)

Where:

is the final amount of the material

is the initial amount of the material (the quantity we are asked to find)

is the time elapsed

is the half life  of cobalt

Knowing this, let's find from (1):

This is the same as:

  (2)

Finally:

>>> This is the amount of grams in the original sample

electrical potential energy =0.072 j

explanation:

electrical potential energy is given by

u= q δv

q= charge=6 c

δv= potential difference and is given by

δv= e d

e= electric field

d= distance=5 mm=0.005 m

δv=2.4 (0.005)=0.012 v

now electric potential energy= u= q δv

u=6 (0.012)

u=0.072 j

0 = 0.40 / 0 = 0

= 0.20 = 9.80 ⁄2 =?

=0 , = = 0.20 =0.50 0 0.40 ⁄

=0−122 =0−12(9.80 ⁄2)(0.50)2 =1.2