# Mass Flow Rate Question

Tags:
1. Aug 3, 2015

### jmine

1. The problem statement, all variables and given/known data
A patient, on an anesthetic, is hooked up with only 18 mg of the anesthetic remaining. If the current flow is 12 mg/h and the dentist needs to increase the flow to 20.0 mg/h within two minutes, then how long will it take for the anesthetic to run out?

2. Relevant equations

mfr = Mass flow rate
mfr = ∆m/∆t

amfr = Acceleration Mass flow rate
amfr = ∆mfr/∆t

3. The attempt at a solution

Last edited: Aug 3, 2015
2. Aug 3, 2015

### tommyxu3

My opinions for reference:
You should pay attention to the $20\text{mg}/\text{h}$ increase and how it increases. Then can see the consumption during these two minutes.

3. Aug 4, 2015

### billy_joule

Is that exactly as stated in the book? It's a little ambiguous...
I'd guess it's attempting to say:

A patient, on an anesthetic, is hooked up with only 18 mg of the anesthetic remaining. the initial flow is 12 mg/h, the dentist gradually increases the flow to 20.0 mg/h over a period of two minutes, then how long will it take for the anesthetic to run out?

4. Aug 4, 2015

### haruspex

Possibly, but to me it sounds more that after two minutes the flow will increase in one step to 20mg/h. Your interpretation has the merit of making the question more interesting.
Is it only the interpretation that's stopping you? If there's more help needed, you must post an attempt.