# Homework Help: What is the specific gravity?

1. Sep 15, 2010

### Raven1972

1. A Cube of lengths 5cm each. The cube weighs .54kg. What is its specific weight?

2. Answers: A)6 g cm3 B)3 g cm3 C) 2.5 g cm3 D) 2 g cm3

3. 5x5x5 = 125cm3 540g/125= 4.32 g cm3 which is none of the above. Could someone verify that I'm correct before I make an idiot of myself when I challenge the question setter?

2. Sep 15, 2010

### Raven1972

I've found out by a process of deduction that the answer is supposed to be 2.5 gcm3.
Is this wrong?

3. Sep 15, 2010

### Staff: Mentor

Specific gravity or specific weight?

If sg - I would say your approach (giving 4.32) is correct. There are possible problems here, like sg being relative to something, not necessarily water - so it doesn't have to be identical to density.

Answers given are strange, as units don't fit neither sg nor sw. Specific gravity should be unitles, specific weight units are N/m3 (more generally force/volume). g/cm3 is wrong - unless it is so called gram-force (9.8 mN) per cm3.

4. Sep 15, 2010

### Raven1972

In this case I believe it supposed to be water

Thanks for the answer. It has confirmed my own conclusions...