Explanation:
1) Initial mass of the Cesium-137=
= 180 mg
Mass of Cesium after time t = N
Formula used :
Half life of the cesium-137 =
= initial mass of isotope
N = mass of the parent isotope left after the time, (t)
= half life of the isotope
= rate constant

Now put all the given values in this formula, we get
Mass that remains after t years.

Therefore, the parent isotope remain after one half life will be, 100 grams.
2)
t = 70 years


N = 35.73 mg
35.73 mg of cesium-137 will remain after 70 years.
3)


N = 1 mg
t = ?

t = 224.80 years ≈ 225 years
After 225 years only 1 mg of cesium-137 will remain.
Answer:
Electrons are found in shells or orbitals that surround the nucleus of an atom. Protons and neutrons are found in the nucleus. They group together in the center of the atom.
Explanation:
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Answer:
chemical change it is melted down
Answer:
50 kg
Explanation:
Data:
Mass of bicycle = 10 kg
F = 168 N
a = 2.8 m/s²
Calculation:
F = ma Divide each side by m, Then
m = F/a
= 168/2.8
= 60 kg
m = mass of bicycle + Naoki's mass. Then
60 = 10 + Naoki's mass Subtract 10 from each side
Naoki's mass = 50 kg