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# Maths Problem watch

1. Hello, I have this problem,

We ventilate a room of volume V m^3 by passing fresh air through it at a rate of Q m^3s^-1. Let c(t) be the concentration of carbon dioxide (Co2) which is measured in parts per 10000, so, eg c=3 means that 3x10^-4 of the air is co2. Let c0 be initial concentration at t= 0 of co2 in room. Cf be concentration of co2 in fresh air. C is a function of time t. c(t).

Using basic concept of rate of inflow – rate of outflow = rate of change.

1. What is the rate of inflow of air.
2. What fraction of this air is Co2
3. What is the rate of inflow of co2 in m^3s^-1.
4. What is the concentration of c02 in the air leaving the room
5. What Is the rate of ouflow of air.
6. What fraction of air leaving the room is co2
7. What is the rate of outflow of co2 in m^3s^-1
8. Write down expression for rate of inflow – rate of outflow = rate of change
9. What fraction of the air in the room at time t is co2
10. what is the volume of co2 In the room at that time.
11. What is the rate of change of this volume
12. Using the result that d/dt(omega c) = (omega) dc/dt where omega is a constant rewrite result in 11.
13. Write down an equation for c which involves dc/dt.

Any help would be much appreciated.
2. (Original post by Donna)
Hello, I have this problem,

We ventilate a room of volume V m^3 by passing fresh air through it at a rate of Q m^3s^-1. Let c(t) be the concentration of carbon dioxide (Co2) which is measured in parts per 10000, so, eg c=3 means that 3x10^-4 of the air is co2. Let c0 be initial concentration at t= 0 of co2 in room. Cf be concentration of co2 in fresh air. C is a function of time t. c(t).

Using basic concept of rate of inflow – rate of outflow = rate of change.

1. What is the rate of inflow of air.
2. What fraction of this air is Co2
3. What is the rate of inflow of co2 in m^3s^-1.
4. What is the concentration of c02 in the air leaving the room
5. What Is the rate of ouflow of air.
6. What fraction of air leaving the room is co2
7. What is the rate of outflow of co2 in m^3s^-1
8. Write down expression for rate of inflow – rate of outflow = rate of change
9. What fraction of the air in the room at time t is co2
10. what is the volume of co2 In the room at that time.
11. What is the rate of change of this volume
12. Using the result that d/dt(omega c) = (omega) dc/dt where omega is a constant rewrite result in 11.
13. Write down an equation for c which involves dc/dt.

Any help would be much appreciated.
What is this? Coursework?
3. 1: Q
4. (Original post by elpaw)
1: Q
Succinct.
5. 2: 0.03 %
6. (Original post by theone)
2: 0.03 %
3. do your own work, or at least show us where u have got up to
7. (Original post by theone)
2: 0.03 %
Isn't it Q*Cf/100 %
8. (Original post by elpaw)
Isn't it Q*Cf/100 %
I thought it meant the air being pumped in.
9. (Original post by theone)
I thought it meant the air being pumped in.
it does; the concentration of co2 in the air being pumped in (which presumably is fresh air) is Cf.
10. (Original post by elpaw)
it does; the concentration of co2 in the air being pumped in (which presumably is fresh air) is Cf.

Substantial

lackluster

hopeless.

regards.

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