Consider a gas enclosed in a box. A molecule of mass m, having a … - Vidyadip

MCQ

Consider a gas enclosed in a box. A molecule of mass $m,$ having a velocity $-2i +3j +4k$ collides with a wall parallel to the $xz$ plane. What will be its velocity after collision and its change in momentum$?\ i, j\ \&\ k$ are unit vectors along the $x, y\ \&\ z$ axis.

✓
$-2i -3j +4k, -6mj$
B
$2i +3j -4k, -6mj$
C
$-2i -3j +4k, 6mj$
D
$2i +3j -4k, 6mj$

✓

Answer

Correct option: A.

$-2i -3j +4k, -6mj$

On collision with a wall parallel to the $xz$ plane, only the $y-$component will change.
Thus, new velocity will be $-2i -3j +4k.$
The change in momentum will be $-3mj -3mj = -6mj.$

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