Math Problem Statement
A tank with a capacity of 1600 L is full of a mixture of water and chlorine with a concentration of 0.0125 g of chlorine per liter. In order to reduce the concentration of chlorine, fresh water is pumped into the tank at a rate of 16 L/s. The mixture is kept stirred and is pumped out at a rate of 40 L/s. Find the amount of chlorine in the tank as a function of time. (Let y be the amount of chlorine in grams and t be the time in seconds.)
Solution
We are tasked with finding the amount of chlorine in a tank as a function of time, , where is the time in seconds, given the following conditions:
- The initial capacity of the tank is .
- The initial concentration of chlorine is .
- Fresh water is pumped in at a rate of .
- The mixture is pumped out at a rate of .
Step 1: Determine the initial amount of chlorine
The initial amount of chlorine in the tank is:
Step 2: Set up the differential equation
Let be the amount of chlorine in grams at time . The rate at which chlorine leaves the tank depends on both the rate of the outflow and the concentration of chlorine in the tank at time .
The volume in the tank is decreasing since more liquid is pumped out than in. The net outflow rate is: So, the volume of liquid in the tank at time is:
Now, the chlorine is being removed from the tank at the outflow rate with a concentration of . Hence, the rate of change of chlorine in the tank is:
Substituting , we get the differential equation:
Step 3: Solve the differential equation
This is a separable differential equation. We can rearrange it as: Integrating both sides: The left side becomes , and the right side can be solved using a substitution. Let , so . This gives: Thus, the solution becomes: where is the constant of integration. Simplifying:
Exponentiating both sides to solve for : Let (a new constant), so:
Step 4: Apply the initial condition
We know that at , . Substituting this into the equation: Solving for : Now we have the complete solution for :
This is the amount of chlorine in the tank as a function of time.
Would you like more details or clarifications on any of the steps?
Here are 5 related questions for further exploration:
- How would the solution change if the outflow rate were reduced?
- How long does it take for the tank to be completely empty of liquid?
- What happens to the concentration of chlorine as time approaches the point where the tank empties?
- How would the equation change if the inflow and outflow rates were equal?
- Can you determine the time at which half of the initial chlorine is removed?
Tip: When dealing with mixing problems, the differential equation often arises from the relationship between the inflow/outflow rates and the concentration of the substance being studied.
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Math Problem Analysis
Mathematical Concepts
Differential Equations
Rate of Change
Separation of Variables
Exponential Functions
Formulas
dy/dt = -40 * (y(t) / V(t))
V(t) = 1600 - 24t
Integral of dy/y = -40 * Integral of dt / (1600 - 24t)
Theorems
Separable Differential Equations
Logarithmic Integration
Suitable Grade Level
Grades 11-12, College Level
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