Question

Dust is removed from hanging carpet when beated by a brush.

Answer 1

This phenomenon is a simple law of inertia.
Inertia is the property of body by virtue of which a body tends to remain in its position of rest or motion.
So is this case in which when we beat the carpet with stick we set the carpet in motion in air while

the dust particles due to their property of inertia tend to remain at rest (since initially they were at rest),

and get separated from the carpet.
Now some of you may think that why doesn't the carpet shows the property of inertia in this case,

it's because when we beat it with stick we apply external force on it while law of inertia holds good

only in the absence of any external force.