Q. A gas molecule of mass $m$ strikes the wall of the container with a speed $v$ at an angle $\theta$ with the normal to the wall at the point of collision. The impulse of the gas molecule has a magnitude
A) $3mv$
B) 2$mv\cos\theta$
C) $mv$
D) Zero
Explanation
(b) From adjoining figure the component of momentum along $x$-axis (parallel to the wall of container) remains unchanged even after the collision.
[image:7_image111.emf]
$\therefore$ Impulse = change in momentum of gas molecule along $y$-axis, $ie,$ in a direction normal to the wall = $2mv$, $= 2mv\cos\theta$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.