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Math help please? Algebra 2?
Carbon-14 decays at a constant rate, so it can be used to determine the age of fossils. In particular, if the original amount of Carbon-14 present is A 0, then A(t) = A 0 e -kt can be used find the amount of amount of Carbon-14 remaining after t years. Given that the half-life of Carbon-14 is 5,730 years, what is the value of the decay constant k to 5 decimal places?
4 Answers
- RogueLv 77 years ago
A(t) = A₀e^(-kt)
A(t) = (1/2)A₀ when t = 5,730 [a half life is how long it takes for half of the original amount to be left]
=> (1/2)A₀ = A₀e^(-5,730k)
divide both sides by A₀
=> (1/2) = e^(-5,730k)
take the natrual og of both sides
=> ln(1/2) = ln(e^(-5,730k) )
given log_a(a^n) = n
=> ln(1/2) = -5,730k
=> ln(2^(-1)) = -5,730k
given log(a^n) = nlog(a)
=> -ln(2) = -5,730k
divide both sides by -5,730
=> k = ln(2)/5,730
=> k = ≈ 0.00012 (5 dp)
note A(t) = A₀e^(-tln(2)/5,730)
=> A(t) = A₀2^(-t/5,730)
- AshLv 77 years ago
Half life of as substance is defined as the time required to reduce the amount of original substance to half .
A(t) = A0 e^-kt
A(5730) = A0 e^-k(5730)
A0 /2 = A0 e^-k(5730)
1/2 = e^-k(5730)
ln(1/2) = -k(5730) ln(e)
k = -ln(1/2)/5730 = 0.00012
- PinkgreenLv 77 years ago
A(t)=A(0)e^-kt
A(5730)=A(0)/2=>
A(0)/2=A(0)e^(-5730k)=>
0.5=e^(-5730k)=>
-5730k=ln(0.5)=>
k=0.00012
- Roger the MoleLv 77 years ago
1/2 = e^(-5730 k)
Take the natural log of both sides:
-0.693147 = -5730 k
Divide by -5730:
k = 0.00012097 = 1.2097 x 10^-4