# I thought conversions were simple

1. Jan 31, 2008

### indepth

I thought conversions were simple, but this one is giving me some trouble. If anyone could help out, it would be greatly appreciated. Thanks in advance.

2. Jan 31, 2008

### hage567

If there are 50 water drops of radius 10 um, what total volume is that?

3. Jan 31, 2008

### indepth

im confused to find volume with only radius..:(

4. Jan 31, 2008

### hage567

What's the volume of a sphere? (The radius is the only thing you need to know)

5. Jan 31, 2008

### indepth

4.18879x10^-10 in meters

6. Jan 31, 2008

### hage567

It's r^3, I think you may have done r^2. The units would be m^3 since it's volume, right?

$$V = \frac{4 \pi r^3}{3}$$

7. Jan 31, 2008

### indepth

sorry, yeah ^3 i did squared. so.. 4.18879x10^-15

8. Jan 31, 2008

### hage567

OK, so what's the volume of a cylinder of height 2.9 km and radius 1.4 km?

The way to approach this problem is to find out how many cubic centimeters there are in the whole cloud. Once you have that, you can figure out how much water there is in the entire cloud because you now know how much there is in one cubic centimeter.

9. Jan 31, 2008

### hage567

Remember to write down your units. That's the whole point of this problem and you will make mistakes if you lose track of them.

So this should be in m^3.

Don't forget to multiply this by 50 to get the total volume of the 50 drops in the cubic centimeter of cloud.

10. Jan 31, 2008

### indepth

in the cylinder, volume is 1.7856x10^10 m^3, right?

11. Jan 31, 2008

### hage567

Yes, that's right.

12. Jan 31, 2008

### indepth

after x by 50 the answer is 2.0949x10^-15. what do i do with the cylinder now?

13. Jan 31, 2008

### hage567

So if there is 2.09x10^-15 m^3 of water for every cm^3 of cloud, how much water is there is 1 m^3 of cloud? (Just convert cm^3 to m^3)

Then, you can find out how much water is in the entire cloud by multiplying by the entire volume of the cloud you just found.

14. Jan 31, 2008

### indepth

2.09x10^-12 per m^3. so now this times 1.7856x10^10 m^3?

15. Jan 31, 2008

### hage567

1 m^3 = 100^3 cm^3. You must cube the 100.

So it should look like $$\frac{2.09x10^-15 m^3 water}{1 cm^3 cloud} * \frac{100^3 cm^3}{1 m^3}$$

Does that make sense?

Last edited: Jan 31, 2008
16. Jan 31, 2008

### indepth

yeah that looks good, i forgot about the cubing of the 100. and now same for the 500 correct? but also. thats not the final is it

Last edited: Jan 31, 2008
17. Jan 31, 2008

### hage567

Yes. What answer did you get?

18. Jan 31, 2008

### indepth

2.09x10^-9 is what i got for the 50. now i will do it for the 500. any idea for part b and or c?

19. Jan 31, 2008

### hage567

Don't forget to multiply by the entire volume of the cloud.

For (b) How many m^3 in a Liter?

For (c), what's density?

Give these a try and see what you can do.

20. Jan 31, 2008

### indepth

3.7319x10^1 correct for 50?

B) .00 m^3
c) p= m/v

Last edited: Jan 31, 2008