# Homework Help: Physics H.W.

1. May 31, 2004

### mustang

Problem 2. Liquid nitrogen, which has a boiling point of
77 K, is commonly used to cool substances to
low temperatures.
How much energy must be removed from
1.4 kg of gaseous nitrogen at 77 K for it to
completely liquefy? Assume the latent heat
of liquid nitrogen is 2.01 *10^5 J/kg Answer
in units of J.

Problem 4.
You have collected exactly 2200 aluminum
cans for recycling, each with a mass of 14.1 g.
How much energy is needed to melt them if
their initial temperature is 26.8 degrees C? Assume
the specific heat, the latent heat and the
melting point of aluminum are 899 J/kg * degrees C,
3.97*10^5 J/kg and 660.4degreesC respectively. An-
swer in units of J.

2. May 31, 2004

### enigma

Staff Emeritus
Mustang,

You've been here long enough to know you should post what you've tried when asking for help.

3. Jun 2, 2004

### Tom McCurdy

how much homework have you done...

4. Jun 2, 2004

### UrbanXrisis

1600J and 3200J

The answers reflect how much effort you put into trying to solving your homework :tongue2: