# Homework Help: Which one is impossible?

1. Jun 13, 2010

### traveler7

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

Which of the following statements are IMPOSSIBLE? Choose all that apply.

___A perfectly functioning hydraulic had a pressure of 36 Pa in the fluid near the small piston and a pressure of 37 Pa in the fluid near the big piston.
___A 35 L container displaced 42 L of orange juice when partially submerged.
___A substance underwent melting during which its temperature remained constant at 33 °C.
___A 37 N brick was fully submerged in water. The buoyant force on the brick was 48 N. As a direct result, the brick was neutrally buoyant.
___Last Friday, the Sun heated the Moon via convection.
___The temperature inside a vacuum chamber was measured to be 3 °C.

2. Relevant equations

3. The attempt at a solution

Based on what I have learned this is my attempt:

_x__A perfectly functioning hydraulic had a pressure of 36 Pa in the fluid near the small piston and a pressure of 37 Pa in the fluid near the big piston.
_x__A 35 L container displaced 42 L of orange juice when partially submerged.
___A substance underwent melting during which its temperature remained constant at 33 °C.
_x__A 37 N brick was fully submerged in water. The buoyant force on the brick was 48 N. As a direct result, the brick was neutrally buoyant.
_x__Last Friday, the Sun heated the Moon via convection.
___The temperature inside a vacuum chamber was measured to be 3 °C.

2. Jun 13, 2010

### Saraphim

Try defining temperature in a perfect vacuum.

3. Jun 13, 2010

### kuruman

So what is your question? Can you provide reasoning why the ones you marked are impossible?

4. Jun 13, 2010

### kuruman

A vacuum chamber does not necessarily hold a perfect vacuum, in fact it never does, not to mention black body radiation.

5. Jun 13, 2010

### Saraphim

You are of course right. I'm too used to idealized questions. :)

6. Jun 14, 2010

### traveler7

well a vacuum chamber has no air,
so would it be 0 K meaning their is no motion in the particles...

so the vacuum one would be impossible too?

My other question is:
is this possible:
A substance underwent melting during which its temperature remained constant at 33 °C

7. Jun 14, 2010

### kuruman

I know plenty of vacuum chambers that have air in them. The statement of the question is
"The temperature inside a vacuum chamber was measured to be 3 °C." There is no mention whether there is gas in it or not. Why do you assume that it contains a perfect vacuum which doesn't even exist?
What happens to the temperature of a substance when it undergoes a phase transition from solid to liquid? Think of melting ice.

8. Jun 14, 2010

### traveler7

I asked my teacher about a vacuum chamber today and he said that it contains no air

and thanks for the other one I understand it now

9. Jun 14, 2010

### kuruman

OK. Assume that the vacuum chamber has not even a single molecule of air. You stick a mercury thermometer in it. Originally the thermometer reads 3 oC. Will the mercury column drop and indicate a lower temperaure?