# Homework Help: Simple question - Archimedes principle

1. Feb 15, 2010

### jayjay112

An object weighs 30kg in air it is lowered into a square tank (1m x 1m)
the weight of the object in the water is 16kg. how much does the water level in the tank raise?

Heres my attempt.
30-16 = 14kg

14kg = 14 m^3

1 x 1 x h = 14

h = 14 metres.

Is this correct it doesnt seem right for some reason??

2. Feb 15, 2010

### Staff: Mentor

Way too much. What is water density?

Last edited by a moderator: Aug 13, 2013
3. Feb 15, 2010

### jayjay112

1000 kg/m^3 = rho

so W/1000 x 9.81 = h?????

=14000/9810 = 1.43m???

Thanks for the help

4. Feb 15, 2010

### Staff: Mentor

Worst approach you can take it to calculate first, apply units later. That's what you are doing and your answer is all the time wrong.

Last edited by a moderator: Aug 13, 2013
5. Feb 15, 2010

### jayjay112

I dont understand? do you mean my formula is correct but my units are wrong?

14/98100= 1.43 x 10^-3???

6. Feb 15, 2010

### Staff: Mentor

What is what of what?

Numbers you present - as long as they don't have any units - don't make any sense.

Last edited by a moderator: Aug 13, 2013
7. Feb 16, 2010

### jayjay112

14kg / (1000kg/m^3 x 9.81m/s)= 1.43 x 10^-3 m

8. Feb 16, 2010

### nasu

I guess the text of the problem creates some confusion. They call the 30 kg "weight" but it's the mass actually.
What is the weight of the water displaced? Not the mass.