# Homework Help: How long will it take to fill a tank?

1. Apr 2, 2012

### ScienceGeek24

1. The problem statement, all variables and given/known data

The water from a pipe flows into a tank of volume 180 m3. If the tank is initially empty, how long will it take to fill the tank?

2. Relevant equations

Q=vA

v1=12m/s
v2=22m/s
A2=0.180982 m2
A1=0.3318 m2

3. The attempt at a solution

This question is the third question from a 3 part problem. In the first two part they were asking me to find the velocity of position 2 of the pipe which is 22m/s, in the second part they were asking me for the diameter of position 2 in the pipe which is 48 cm and in this third part they are asking me how long does it take to fill in the tank with 180 m3.

My attempt was using volumetric flow, but which end should I use? v1a1 or v2a2 since they don't mention where is the tank located at.

any hints to where to start from?

2. Apr 2, 2012

### Villyer

How does v1a1 compare to v2a2?

3. Apr 2, 2012

### ScienceGeek24

Hmmm can you be more specific?

4. Apr 2, 2012

### Villyer

You mentioned using the volume flow rate to find the answer, but is the volume flow rate at position one different than volume flow rate at position two?

5. Apr 2, 2012

### ScienceGeek24

ah! so it really doesnt matter which end i use because they are both going to have the same volumetric flow???

6. Apr 2, 2012

### ScienceGeek24

however, is volumteric flow correct to approach this problem?

7. Apr 2, 2012

### Villyer

Exactly! All points along a point have the same volumetric flow, therefore you can choose any point you desire.

And what is the equation and units for volumetric flow?

8. Apr 2, 2012

### ScienceGeek24

Q=vA= (12 m/s)(0.3318 m2)= 3.98 m3 s-1

and the equation is Q=V/t???

9. Apr 2, 2012

### Villyer

Right! Can Q=V/t be used to answer the question?

10. Apr 2, 2012

### ScienceGeek24

yep just got it!! 45.2 secs thanks!!

11. Apr 2, 2012

### Villyer

No problem, good luck with the rest of your physics.