# Water Density Question

Discussion in 'Community Discussion' started by mac000, Aug 12, 2008.

1. ### mac000 macrumors 6502a

Joined:
Sep 6, 2005
#1

Assume for a moment that five inches of snow ended up falling at a college. Your instructor goes out to shovel his 40-feet by 10-feet driveway, which is covered in a five- inch thick blanket of white. Assuming that a heavy, wet snow fell at the college (at a snow-water ratio of 7:1), how much would the snow on the driveway weigh? Now assume a dry, fluffy, powdery snow,with a snow-water ratio of 20:1. How much would five inches of this type of snow weigh on the driveway?

2. ### Chundles macrumors G4

Joined:
Jul 4, 2005
#2
Give the question to me in metric and I'll give it a go.

3. ### swiftaw macrumors 603

Joined:
Jan 31, 2005
Location:
Omaha, NE, USA
#3
So that is (40*12)*(10*12)*5 = 288000 cubic inches of snow

A 7:1 snow-water ratio means that this equates to (288000/7) = 41182.86 cubic inches of water

The mass of 1 cubic inch of water is 0.036127 pounds

So 41182.86 cubic inches of water weighs approx 1486.4 pounds

Repeat for the fluffy 20:1 ratio snow.

4. ### oldschool macrumors 65816

Joined:
Sep 30, 2003
#4
convert everything to similar units. Let's use inches.
40' = 480"
10' = 120"

• VOLUME OF SNOW: 480*120*5 = 288 000 cu. inches

• 1 cu. inch of water becomes 7 cu. inches of snow (snow is less dense)

• (288 000 cu. in. snow)/(x sq. in. water) = (7 cu. in. snow)/(1 cu. in. water)

• CROSS MULTIPLY and solve for X

• This will give the volume of water in the driveway in cu. in. Now you have to figure out the weight of one cu. in. of water.

I just looked it up on google: Water is 0.036127 pounds/cu.in.

If the question was in metric it would be a lot easier, since at sea level, one cubic centimeter of water is equal to one gram.

Good luck.

5. ### swiftaw macrumors 603

Joined:
Jan 31, 2005
Location:
Omaha, NE, USA
#5
Umm, I did just that above.

6. ### EricNau Moderator emeritus

Joined:
Apr 27, 2005
Location:
San Francisco, CA
#6
At sea level? Would that make a difference?

Temperature, on the other hand, would make a difference; one cc of water is equal to one gram at approx. 4 degrees C, I believe.

7. ### oldschool macrumors 65816

Joined:
Sep 30, 2003
#7
ever think that i opened the window before you posted? i posted mine just a few minutes after yours. SORRY.

plus mine looks better with the bullet points and all.

8. ### swiftaw macrumors 603

Joined:
Jan 31, 2005
Location:
Omaha, NE, USA
#8
Yeah, I was never one for presentation

I could also argue that it is mass not weight that the OP is finding. Weight depends on location, mass doesn't.

9. ### notjustjay macrumors 603

Joined:
Sep 19, 2003
Location:
#9
So.... why are we helping do somebody's homework?

10. ### Abstract macrumors Penryn

Joined:
Dec 27, 2002
Location:
Location Location Location
#10
Americans have to remember that to do basic maths/physics?

I quite enjoy the metric system, where density of water is 1 g/cm^3.

Joined:
Sep 6, 2005
12. ### EricNau Moderator emeritus

Joined:
Apr 27, 2005
Location:
San Francisco, CA
#12
No, because in physics we use the metric system as well.

Joined:
Oct 11, 2004
Location:
On the Left Coast - Victoria BC Canada
#13
I'll keep that in mind next time I'm shoveling snow on Mars.

14. ### Rodimus Prime macrumors G4

Joined:
Oct 9, 2006
#14
not really. My method is I remember a handful of basic things. Like 1 cm^3 happens to be 1 ml of water and also happens to be 1 gram.

From there I can easy converted around. I know a handful of basic unit conversions and it is a cake walk.

Everything can be messed around from there.

In school I had to jump around between systems all the time and I just got used to it. Mind you in my engining classes I spent most of my time in the American system but mind you the loads I was dealing with where measured in kips. Hell I still used kips today in talking about some loads but mostly everything in in tonnage.

Lastly it is not as bad as it seems you just get used to it.

no he is right. Temperature and pressure both effect the denenty of water.

Water is always approx 1 gram/cm^3 but really it = 1 g/cm^ only at STP (standard temp and pressure) which I want to say is 4C at sea level.

water is far from the ideal liquid and steam is far from being ideal gas.

15. ### Abstract macrumors Penryn

Joined:
Dec 27, 2002
Location:
Location Location Location
#15
Thank goodness there are science teachers in America, then.

But to be honest, I knew the speed of light in miles/hour before I ever knew it in km/h, but that's because I read it it in a book or something when I was 9 or 10 years old, when I didn't even know there was a US imperial system (and one that's slightly different than the one that was used in the UK....)

16. ### EricNau Moderator emeritus

Joined:
Apr 27, 2005
Location:
San Francisco, CA
#16
That's funny, because I only know the speed of light in meters/sec.

...Having just looked it up, how can you possibly remember 670,616,629.4 mph?

In theory, yes, but I don't believe differences in altitude would account for any change in volume. Water has a bulk modulus of over 2e+9 Pa, so it changes very little with increased pressure. All liquids, in fact, are virtually not compressible.

STP is 0 degrees C at 100 kPa, at which water is ice, making it less dense than 1 g/cc.