Math Problem Statement

A biologist has a 9568-gram sample of a radioactive substance. Find the mass of the sample after five hours if it decreases according to a continuous exponential decay model, at a relative rate of 15% per hour.

Solution

This is a problem involving exponential decay. The decay model for a continuous process can be described by the formula:

M(t)=M0ektM(t) = M_0 e^{-kt}

Where:

  • M(t)M(t) is the mass remaining after time tt,
  • M0M_0 is the initial mass,
  • kk is the decay constant (relative rate of decay),
  • tt is the time,
  • ee is the base of the natural logarithm.

Given:

  • M0=9568M_0 = 9568 grams (initial mass),
  • k=0.15k = 0.15 (15% per hour decay rate),
  • t=5t = 5 hours.

We need to find M(5)M(5), which is the remaining mass after 5 hours.

Step-by-step Calculation:

  1. Apply the values to the exponential decay formula:

M(5)=9568×e0.15×5M(5) = 9568 \times e^{-0.15 \times 5}

  1. Simplify the exponent:

M(5)=9568×e0.75M(5) = 9568 \times e^{-0.75}

  1. Use e0.750.472e^{-0.75} \approx 0.472:

M(5)=9568×0.472M(5) = 9568 \times 0.472

  1. Multiply:

M(5)4516.1gramsM(5) \approx 4516.1 \, \text{grams}

Thus, the mass of the sample after 5 hours is approximately 4516.1 grams.

Would you like further details or explanations on any step?

Here are 5 related questions for further exploration:

  1. How would the remaining mass change if the decay rate was 10% per hour?
  2. How can we derive the decay constant if we know the half-life of a substance?
  3. How much mass would remain after 10 hours with the same decay rate?
  4. What happens to the sample's mass as time approaches infinity?
  5. Can you solve a similar problem using a discrete decay model instead of a continuous one?

Tip: Always check whether a decay process is continuous or discrete, as the formulas vary for each model.

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Math Problem Analysis

Mathematical Concepts

Exponential Decay
Calculus
Natural Logarithms

Formulas

M(t) = M0 * e^(-kt)
Exponential Decay Formula

Theorems

Exponential Growth and Decay Theorem

Suitable Grade Level

Grades 10-12