Question

A specific radioactive substance follows a continuous exponential decay model. It has a half-life of 16 days. At the start of the experiment, 65.7 g is present.

(a) Lett be the time (in days) since the start of the experiment, and let
y be the amount of the substance at time t.
Write a formula relating y to t.
Use exact expressions to fill in the missing parts of the formula.
Do not use approximations.
y = ei
(b) How much will be present in 13 days?
Do not round any intermediate computations, and round your
answer to the nearest tenth.
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Oina
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Answer 1

Answer: (a) The formula relating the amount of substance, y, to time, t, is given by:

y = y₀ * e^(-λ*t)

where y₀ is the initial amount of the substance, λ is the decay constant, and e is the mathematical constant approximately equal to 2.71828.

The half-life, T½, is related to the decay constant as:

T½ = ln(2)/λ

We are given that the half-life of the substance is 16 days, so we can solve for λ:

λ = ln(2)/T½ = ln(2)/16

Substituting this value of λ in the formula for y, we get:

y = 65.7 * e^(-ln(2)*t/16)

(b) To find the amount of substance present after 13 days, we substitute t = 13 in the formula for y:

y = 65.7 * e^(-ln(2)*13/16) ≈ 42.1

Rounding to the nearest tenth, we get y ≈ 42.1 g. Therefore, approximately 42.1 g of the substance will be present after 13 days.

Explanation:

Answer 2

Explanation:

(a) Lett be the time (in days) since the start of the experiment, and let

y be the amount of the substance at time t.

Write a formula relating y to t.

Use exact expressions to fill in the missing parts of the formula.

Do not use approximations.

y = ei