Chemistry

Problem

A beam of helium atoms, each of mass

6.6\times10^{-27}\,\text{kg}

, travels through a vacuum and strikes a flat wall of area

1.0\,\text{m}^2

. All atoms move at

4.0\times10^{2}\,\text{m\,s}^{-1}

and approach the wall at an angle of

60^{\circ}

with respect to the wall’s normal. The number density of atoms in the beam is

1.0\times10^{22}\,\text{m}^{-3}

, and collisions are perfectly elastic. Neglect interactions among atoms. What is the pressure exerted on the wall by the beam? a)

1.1\times10^{1}\,\text{Pa}

2.6\,\text{Pa}

5.3\,\text{Pa}

2.1\times10^{1}\,\text{Pa}