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olga_2 [115]
3 years ago
13

A mass of 100 grams of a particular radioactive substance decays according to the function m(t)=100e−t850

Physics
1 answer:
AleksandrR [38]3 years ago
8 0

Answer:

After 1023.4 years the mass of the substance will be 30 g.

Explanation:

Hi there!

Let´s write the function (according to what I found on the web):

m(t) = 100e^{-t/850}

We have to find the time "t1" at which the mass of the substance is 30 g. Mathematically:

m(t1) = 30

Then:

30 = 100e^{-t1/850}

Let´s solve the equation for t1. First, divide by 100 both sides of the equation:

0.3 = e^{-t1/850}[/tex]

Apply ln to both sides of the equation:

ln(0.3) = ln(e^{-t/850})

Use the logarithm property: ln (aᵇ) = b ln(a)

ln(0.3) = -t/850 · ln (e)             (ln (e) = 1)

ln(0.3) = -t/850

850 ln(0.3) = -t

t = -850 ln(0.3)

t = 1023.4

After 1023.4 years the mass of the substance will be 30 g.

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