# Homework Help: Kinetic energy of neutron

1. Sep 24, 2010

### louza8

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

Suppose you want to observe neutron diffraction in a crystal with 0.27nm spacing between lattice planes.

Part A asks for the momentum of neutrons with a wavelength equal to the spacing. I used p = h/lambda to get the correct answer 2.5×10−24kgms-1

Question1:

Find the kinetic energy of neutrons having wavelength equal to this spacing.

Question2:
If these neutrons constituted an ideal gas, what would be the gas temperature?
2. Relevant equations

Q1. k=0.5mv2
Q2. PV=nRT
3. The attempt at a solution
Q1: I've tried a couple of different methods, dunno if i'm going the right way with this.
k=0.5mv2
0.5(1.67*10^-27)(1.47*10^3)^2 = 1.80*10^-21J

is this correct?
Q2: I have no idea.

Last edited: Sep 24, 2010
2. Sep 24, 2010

### ehild

Q1 is correct.

What is the average kinetic energy of an atom or molecule in an ideal gas?

ehild

3. Sep 24, 2010

### louza8

Ah, cool.

so 0.5mv^2 = (3/2)kT? So just rearrange to get T with k being boltzmann's constant?

4. Sep 25, 2010

### ehild

I hope it is that easy. Try.

ehild

5. Sep 26, 2010

### louza8

correct, thanks